In the not-too-distant future, former pro-boxer turned robot-boxer trainer/fighter, Charlie Kenton, (Hugh Jackman) drives his box-truck through rural Texas. He arrives at a county fair, parks his truck, and sleeps. The next morning he is awoken by a phone call - one of his many creditors is looking to collect some money Charlie owes him. Charlie fakes that his phone is dying and blows the creditor off. Three young girls appear at the rear of his truck, wishing to see his robot fighter "Ambush" - a blue, rusty fighting bot that has seen better days. Charlie offers to let them take photos of Ambush for $5. The girls roll their eyes and leave without photos.
Charlie is getting ready for his match - Ambush vs. an 800 lbs. bull. He arrives at the small rodeo ring to find that the bull weighs closer to 2 tons. Charlie demands to speak with the man in charge. Former boxing opponent and bully Ricky (Kevin Durand) owns the venue and tries to convince Charlie to fight his bot anyway. He wagers that if Ambush can beat the 2 ton bull, he will pay Charlie $20,000. However, if Charlie loses, he'll owe Ricky the same amount. Money-hungry, Charlie agrees to let the fight take place.
Ambush and the bull fight. Ambush is controlled by Charlie, who stands in one corner controlling the bot with an elaborate remote control harness. Ambush initially bests the bull. However, when Charlie is distracted by a pretty woman in the stands, the bull rips off one of Ambush's legs, sending it flying into the stands. Charlie, now flustered, attempts to beat the bull with a one-legged Ambush, but fails. Ambush is gored to pieces by the bull before Ricky rings the bell. The trio of little girls, from before, stomp out of the arena with Ambush's severed leg as a souvenir. Charlie demands that they return it; the girls offer to sell it back to him… for $5. Charlie, now owing Ricky $20,000 sneaks back to his truck, and is about to drive off when he is accosted by two men in suits. Assuming that they're Ricky's men, Charlie decks one and jumps into his truck, until the other announces that they aren't Ricky's goons, but rather court-appointed messengers with a summons. They tell him that Charlie's former girlfriend and mother to his estranged son, Max, has died. He needs to appear in court to contest the parental custody of his kid. Charlie sneaks away from the fair without paying an angry Ricky.
Max Kenton (Dakota Goyo) sits in a court waiting room while his rich Aunt Debra (Hope Davis) and Uncle Marvin (James Rebhorn) sit in front of a judge to contest Charlie's parental rights. Debra was Max's mother's sister, and wishes to retain sole rights over Max… at any cost. Charlie arrives to the hearing late and wishes nothing more than to sign some paperwork and give up his rights to Max, however, upon seeing Debra and Marvin's expensive clothing and jewelry he hatches a plan. With Marvin in earshot, Charlie pretends to call an orphanage where he would abandon Max. Marvin overhears the conversation and after a quick negotiation, will pay Charlie $100K to sign Max over to him and Debra, as long as Charlie can watch him for three months while the two honeymoon in Italy. Charlie agrees, as long as Marvin pays him $50K now and $50K when they return from Europe. Charlie receives another phone call from a robot-boxing associate, who is looking to unload a once-famous fighting robot named "Noisy Boy" who's spent the last ten years fighting all over the world. The asking price is $45K - Charlie eagerly accepts the offer and tells the man to drop off Noisy Boy at Tallet's gym.
Charlie meets Debra, Marvin and Max at his old training gym owned by his old friend Bailey Tallet (Evangeline Lilly), the daughter of his old boxing coach who has since passed away. Marvin gives Charlie the $50K and delivers the clearly unhappy Max, before leaving. Max demands that Charlie give him half of the money, for "selling him." Charlie refuses, saying that he's already spent the money on a robot. Both head inside, and with Bailey's help, they unload Noisy Boy from his shipping crate. Giant, purple, and covered in glowing yellow Japanese characters, Noisy Boy is imposing. Using Noisy Boy's voice-command feature, Charlie attempts to command the robot to throw some jabs. Noisy Boy speaks Japanese, a language spoken by Max, which he learned by playing video games. They change the bot's language to English and try out some of Noisy Boy's more rudimentary fighting commands. While Charlie tests Noisy Boy, Max talks with Bailey, who reveals that Charlie was once a great boxer. His most shining fight was when he was an unknown in 2007. He was supposed to be a nothing warm-up fighter for the second best boxer in the world, but nearly defeated the runner-up in battle. She gives Max a newspaper trimming detailing Charlie's near win. Charlie heads directly to the underground robot-fighting arena, with Max in tow. At the arena Charlie meets with fight promoter, and old friend Finn (Anthony Mackie). Finn is pleased to see that Charlie has brought a notorious robot to fight with, but only wants Charlie to fight in some low-tier matches. Charlie refuses, saying that he wants to make money fast and wants to fight local champion Midas, much to the disappointment of Max.
The match begins, and Noisy Boy, while powerful, is difficult to control. Charlie completely loses control of Noisy Boy and can only watch while it is pummeled. Midas lops one of its arms off and beats it into submission before completely destroying it. A visibly angry and short-tempered Charlie tells Max to get in the truck while he loads the remains of Noisy Boy in the back. Charlie is out $45K and sells Finn Noisy Boy's head for $400 - which he hangs over the entryway of the fighting arena. Charlie, still needing to earn cash, tells Max that the only thing they can do is build their own bot using scrap and fight in non-league bouts.
The two arrive at a public recycling center. Charlie breaks the lock, and they sneak in. They avoid security detection and ultimately arrive at a portion of the junkyard with busted androids. Charlie chastises Max for standing too close to a muddy cliff, before watching as the ground gives way beneath him, sending him careening down a slippery slope. Charlie chases after Max and finds him dangling over a huge chasm, saved by the outstretched inanimate hand of a robot jutting out of the mud. Charlie pulls Max back onto the ground and tells him that they have to get out of there. Max refuses, saying that the robot saved him and that he wants to unearth it and keep it. Charlie, clearly stressed out, tells the kid that he won't help him and returns to the van while Max digs the android out of the mud.
The next morning Max tugs a trailer, carrying the muddy, inoperable droid back to Charlie's truck. Charlie laughs at the kid's tenacity, but points out that the robot is old and small. Max doesn't care. The two head back to Tallet's gym where Bailey is having a hard time paying the bills. She and Charlie sift through the remains of Ambush and Noisy Boy but find very few salvageable pieces. She tells him that if he can't pay her the money he owes her, she'll have to sell her dad's gym. They bring in the muddy droid and turn on his power supply. To their surprise the droid awakens and stares at the three of them, and begins copying their various body movements with a "shadow-mode." Bailey theorizes that this robot is a second-generation sparring bot whose purpose was to mimic the actions of the stronger robots that it would practice against. It's heavily armored, but too small and weak to deal out legitimate damage. Max is undeterred; he found the robot and he wants Charlie to get it a fight. Charlie tells the kid to go wash it off. Max takes it out back and hoses it off, revealing under the mud, on its chest-piece, a carving of the name "ATOM." Max and Atom jog through the neighborhood, knocking over dumpsters and fire hydrants along the way.
The three pile into Charlie's van and hit the road. Charlie tells Max that he has a friend that should be able to get him a new fighting-bot to replace Noisy Boy. The two arrive at a massive arena in Atlanta. The arena's marquee flashes images of the greatest fighting bot to ever fight - Zeus. Tall, jet black with green lighting, unbeaten, untouched, untouchable. Charlie tells Max to wait near the entrance while he goes to speak with his friend. Charlie meets with Finn and begs him for a second chance. Finn laughs, telling Charlie that he is a bad bet, but recommends that he take his junkyard bot to "The Zoo" and make a few bucks there. Meanwhile, Max, who has strayed from the entrance, catches a glimpse of Zeus exiting his latest fight. Reporters swamp the room, peppering Zeus' owner Farra Lemcova (Olga Fonda) and designers Tak Mashido (Karl Yune) with questions. They laugh off all contenders and Max is mesmerized by Zeus. Charlie catches up with Max, annoyed that he ran off, and tells him that he got a fight for Atom.
The next day, Charlie and Max arrive at a defunct zoo where illegal robot fights take place. A punk-rock, mohawked bot-fighter challenges Max and Charlie - if Atom can last through the end of the first round, he'll pay them $1K. If Atom can make it through the second round, he'll pay $2K. The fight begins. Atom's opponent is easily twice his size, but is unbalanced and cobbled together from pieces from other robots. Atom is knocked down multiple times, but demonstrates his unparalleled ability to take a punch. He gets back to his feet, beating the referee's clock every time. With Max controlling Atom and Charlie giving him boxing-advice, Atom is able to avoid the monstrous bot's swings and delivers a punch that knocks it out of commission. The mohakwed fighter gives Max the money, and as the two leave with Atom they're offered another fight later that week.
Max excitedly upgrades Atom - giving him Noisy Boy's voice recognition feature, enabling him to fight without the need of a remote control. As they rest at a hotel, Max teaches Atom how to dance, using the shadow-mode feature which elicits applause from Charlie. Max is embarrassed. Charlie tells Max that a dancing robot is a nice hook; a way to add some flair to the team. He bows to Max's requests and says if Max teaches Atom how to dance, and maintains his circuitry, Charlie will teach Atom how to box. The two visit, and win more and more barroom and parking lot fights. Atom's popularity is reaching the airwaves, and bringing out big crowds wherever he fights. After one fight, Charlie and Max are approached by a recruiter for the Professional Robot Boxing League. He wants Atom to fight "Twin Cities" at a sanctioned event in Detroit. Charlie and Max are beyond excited.
The team arrives at the event in Detroit and are invited to meet with Farra Lemcova in the Zeus suite. Farra offers them $200K to purchase Atom as a sparring robot for Zeus. Charlie wants to sell Atom, but Max doesn't. Farra tells them that the offer comes off the table when the Atom/Twin Cities fight begins. Twin Cities is a two-headed, very strong fighting bot with incredible reach and duel operators. Atom is quickly boxed into a corner while Charlie frantically commands to escape. Charlie searches Twin Cities for a weakness…. and finds it: whenever the robot reaches back to punch, it reveals an unprotected spot on its torso. Charlie times his blows correctly and pushes Twin Cities back before completely KO'ing Twin Cities. As the fans mob the ring, Max jumps into the center and wrestles the mic away from the announcer. He teases Farra for trying to buy Atom, and calls out Zeus for a fight. Farra and Tak stand in the owner's box, seething with anger. The crowd goes nuts; all are rooting for Max and Atom.
As Max and Charlie box up Atom and prepare to leave, Ricky arrives, with a pair of goons and they assault Charlie. Charlie repeatedly attempts to pay Ricky the $20K he's owed, but Ricky wants to beat Charlie within an inch of his life. During the skirmish, Max attempts to wrestle a goon off of his Dad, but is smacked around and robbed of his winnings. Ricky leaves Charlie coughing and sputtering on the ground before taking all of his money and leaving with his men. Charlie realizes the danger of keeping Max with him and calls Debra. Charlie takes Max to see them and despite his objections, Max leaves with Debra and Marvin. Charlie returns to Tallet's gym to see Bailey. There, he is reminded of his fatherly duties and returns to Debra's home. He sees Max and promises to be a better father than he was before. He asks, and receives Debra's permission to take Max to Atom's fight with Zeus.
Outside the arena, Finn is accepting bets from all takers on the fight. Odds are heavily favored toward Zeus. Ricky arrives, with his date, and bets $100K that Atom won't make it through the first round. He gives his seat information to Finn, who eagerly accepts the wager.
Charlie and Max prepare Atom for the big fight. Atom is the clear underdog; he is smaller, and has less reach and strength. Zeus is undefeated and has a reputation for knocking out opponents with the first hit.
Team Atom humbly enters the arena and watches as Zeus reaches the outer ropes and leaps up and over them, frightening Charlie. Charlie and Max watch from the corner as the fight begins. Zeus lands the first punch and puts Atom on the ground. The referee begins his count, and Atom gets to his feet before he can reach 10. Zeus punches him down again, and a third time. Atom gets to his feet every time, and despite being heavily damaged and smoking, Atom survives the first round. Ricky is shocked, and hastily tells his date that they have to leave, but are cornered by Finn and his men as he attempts to flee. He is forcibly removed from the arena by Finn.
As round two begins, Zeus is as powerful as ever but is caught off guard by a few powerful punches landed by Atom. The entire stadium, and Tak, are shocked. Not only has Zeus never lost a fight - he's never taken a hit. The round is heavily favored to Zeus, but a few well-timed blows by Charlie and Atom upset Zeus' confidence. The round ends with both bots standing and Atom in need of serious repair. Max opens his back panels revealing frayed and smoking wiring which they hastily repair.
In the third round, Charlie and Atom continue to chip away at Zeus' shell and dole out just as much damage as they receive.
As the fourth round begins Zeus pummels Atom's head, destroying his aural systems, rendering him incapable of receiving verbal commands from Charlie. Atom simply slumps in the ring corner as Zeus bashes him nonstop until the bell rings. Atom is severely damaged, but is still in one piece. Without a functioning verbal command system, Max tells Charlie that they'll have to switch him to shadow mode and that Charlie will have to visibly throw punches in the final round and that Atom will copy his movements. Charlie reluctantly accepts the charge and tells Atom to always keep his eyes on him.
The round begins and with Charlie's near precognitive ability to tell what Zeus' next blow will be, he and Atom are able to avoid most of Zeus' blows and knock Zeus down to the mat, shocking the crowd and Tak. Tak angrily takes control of Zeus as the ref counts. Zeus gets to his feet, and Atom delivers more crushing blows but is stopped short of KO'ing Zeus by the ref's bell. As there was no visible winner in the five rounds, the decision will go to the judges. Zeus barely squeaks out a victory, on points, but his team is unhappy. Tak flees the arena while Farra appeals to the crowd, who boos in response.
As Zeus' team exits the arena, the announcer proclaims that Atom is the "People's Champion" which garners a huge cheer from the audience. Charlie and Max cheer as Bailey, Debra, and Marvin look on the from the stands.
You can send in your spoiler to other movies by going here.