Synopsis
In 2020, human boxers have been replaced by robots. Charlie Kenton (Hugh Jackman), a former boxer, owns the robot Ambush. He enters his fighter in unsanctioned matches and exhibition fights. At a county fair, Ambush is destroyed by a bull belonging to promoter Ricky (Kevin Durand). Having made a bet that Ambush would win, Charlie now owes Ricky $20,000, money he doesn't have, so Charlie has to run away.
Charlie is told his ex-girlfriend has died, and that he must attend a hearing about the future of his son Max (Dakota Goyo). Max's wealthy aunt and uncle (Hope Davis and James Rebhorn) want full custody, which Charlie gives them for $100,000, half in advance, on the condition that Charlie takes Max for three months while the couple are away on a second anniversary.
Charlie and Max meet Bailey Tallet (Evangeline Lilly), a friend of Charlie's who runs her dad's boxing gym, Charlie's old coach. Charlie buys a secondhand World Robot Boxing league (WRB) robot, the once-famous Noisy Boy and arranges for it to fight the illegal circuit's champion, Midas. The fight starts well for Charlie, but due to both his inexperience with Noisy Boy's controls and his own overconfidence, Charlie ends up losing control of Noisy Boy and Midas destroys it.
Charlie breaks into a junkyard with Max to steal scraps that he can use to build a new robot. Max falls over a ledge, where he is saved by getting snagged on the arm of a buried robot. After Charlie pulls Max up, Max digs out the entire robot and calls him Atom. Charlie takes it back to Bailey's gym to overhaul it. They discover Atom is an obsolete Generation-2 sparring bot from 2014. Atom was designed to sustain massive damage. Atom also has a "shadow function" which allows him to follow or copy human movement. Max insists and Charlie agrees since he needs the money, on having Atom fight an unsanctioned match against the robot Metro. Atom wins, earning back some of Charlie's money.
Max later upgrades Atom to take vocal commands, using parts from Charlie's old robots, and convinces Charlie to train Atom. Atom's later string of wins attracts the WRB's attention, and they offer Atom a professional fight against the robot Twin Cities. Charlie accepts and Atom wins again, thanks to Charlie's boxing experience allowing him to take advantage of a small tell in Twin Cities' punch. Reveling in the attention, Max challenges WRB champion Zeus, designed by genius Tak Mashido (Karl Yune) and sponsored by wealthy Farra Lemkova (Olga Fonda), a woman who wants to monopolize the robot-boxing industry. She even tries to buy Atom that evening.
Ricky, who had bet $100,000 that Atom would not last the first round, tries to slip away, but is cornered by the bookie and his colleagues. In the fourth round of the five-round match, Atom's controls are damaged, and Atom must fight in shadow mode, copying Charlie's moves. Zeus, now controlled manually by a furious Mashido, tries to overpower Atom, running low on power and becoming sluggish. The fight swings in Atom's favor as he overwhelms the weakened Zeus, even knocking the champion down, but Atom is unable to win before the fight ends. The judges declare Zeus the winner on points, but the near-defeat leaves the Zeus team humiliated. The people cheered for Atom, who is labeled the "People's Champion" as Charlie and Max celebrate their success together as father and son.
