We begin with Charlie, portrayed by Hugh Jackman, who navigates the countryside while hauling a trailer to a local fair. He is set to pit his old robot Ambush against an imposing 800-pound bull. However, the ringleader deliberately alters the terms of the match, presenting a fierce 2,000-pound bull instead. Despite this setback, Charlie and Ambush strive valiantly until Charlie's attention is diverted by a girl in the stands. Seizing this opportunity, the bull charges at Ambush, damaging its leg. The resilient robot attempts to rise on one leg, but is ultimately no match for the bull's strength.
With more money wagered than he can afford, Charlie flees the scene to escape the mounting debt. Meanwhile, his son Max, who was living with his mother, faces a transition after her passing. Texas law dictates that custody must revert to Charlie. Although his aunt is willing to care for Max, Charlie resorts to blackmailing her wealthy husband for $100,000 to finalize the custody papers. After receiving half of the sum upfront, Charlie invests in a vintage champion bot named Noisy Boy. With the assistance of his son and Bailey, played by Evangeline Lilly, who is both his former love and the daughter of his boxing coach, he attempts to train Noisy Boy. Yet, due to his unbridled enthusiasm, Charlie skips essential training, leading to a hasty fight that ends in devastation—not only does he lose the match, but also his prized bot.
After this setback, Charlie and Max scour a junkyard for parts, where a near-disaster leads Max to discover a buried robot. However, Charlie disregards its potential, telling Max to dig it up for a second chance. Undeterred, Max spends the night excavating the robot. When they start the bot, they discover it possesses a rare Shadow Function, a feature Charlie cannot see the value in, while Max recognizes it as a remarkable machine. This second-generation robot, primarily crafted for sparring with higher-class bots, lacks the design for direct combat. After a failed attempt to secure a loan, Max finally persuades Charlie to allow them to utilize the robot in a match. Throughout the night, they develop a bond with the robot, whom Max names Atom.
They venture to The Zoo, an underground fighting ring, where drugs and rules are absent. Ignoring Charlie's objections, Max places a bold bet against the ringleader, leading to a stunning underdog triumph. Riding the wave of success, they set up subsequent fights. While training Atom, Max discovers that the bot can replicate dance moves using its shadow function, ultimately leading Charlie to agree to incorporate this into their fighting strategy, fostering roles where Max acts as the showman while Charlie teaches Atom to fight.
With Atom showcasing incredible resilience and agility, their fame begins to rise. After multiple victories, they catch the attention of promoters, earning an invitation to participate in the Worldwide Robot Boxing (WRB) competition. Their first match pits them against Twin Cities, a bot with dual controllers. In a tension-filled confrontation, Charlie identifies Twin Cities' vulnerabilities, guiding Atom to a victorious conclusion. In a surge of enthusiasm, Max dares to challenge Zeus, the reigning champion bot, known for annihilating every opponent it faces.
As their fame grows, Charlie's past mistakes resurface when the menacing debt collectors from the county fair confront him. They assault Charlie and threaten Max, which sends Charlie reeling. Realizing the peril they face, he resolves to send Max away for his safety. An emotional exchange occurs as Max reveals he merely craved his father's support. After careful thought, Charlie decides to reconcile and prepare for the monumental fight against Zeus.
On the day of the championship match, Atom faces dire odds—5 to 1 against survival. As the battle commences, Zeus swiftly knocks Atom down. However, Charlie casts aside the automatic commands, opting for a personal fighting style. Despite substantial assaults, Atom endures beyond what previous bots managed against Zeus. Surprising strikes from Atom during the second round disrupt Zeus’s automated balance, allowing Atom to gain momentum as the fight progresses.
As they near the end of the fourth round, Atom becomes cornered, causing its voice recognition to fail. With Zeus poised to conclude the bout, the bell rings just in time, sparing Atom from defeat. Inspired by Max, Charlie taps into the shadow function, employing Atom's unique agility in a final retaliatory effort. Exchange after exchange, Atom pushes forward, delivering powerful blows to Zeus, prompting frustration from Zeus's creator. Even as Zeus's program is manually overridden, Charlie leverages the shadow function to maintain their offensive.
As the final round concludes, despite an overwhelming effort, the judges award Zeus the victory, yet Atom earns the prestigious title of "People's Champion," cementing their legacy within the sport.
