In Russia, the national media broadcasts footage of Tony Stark publicly declaring himself as Iron Man. Watching this moment is aging physicist Anton Vanko, who lies on his deathbed. In his final moments, he tells his son, Ivan Vanko, that their family’s legacy was stolen by Howard Stark. He leaves Ivan with nothing but his knowledge—blueprints for the Arc Reactor—and instills in him a deep sense of injustice and entitlement. This becomes the seed of Ivan’s revenge.

Six months later, Tony Stark has become a global celebrity. He openly operates as Iron Man, using his advanced suits to maintain world peace. Governments, however, are uneasy about one man holding such power. At the grand reopening of the Stark Expo—an event inspired by his father Howard Stark—Tony celebrates innovation and legacy. Yet behind the confidence, he is hiding a fatal secret: the palladium core powering the Arc Reactor in his chest is slowly poisoning him. The very device keeping him alive is killing him, and no alternative element has been found.

Soon, Tony is summoned to Washington, D.C. to testify before a Senate Armed Services Committee led by Senator Stern. There, rival industrialist Justin Hammer argues that the Iron Man technology should be turned over to the military. Tony refuses, asserting that he is Iron Man—that the technology cannot be separated from him. To prove his point, he exposes failed attempts by foreign governments and even Hammer himself to replicate the suit, humiliating his competitors. Despite his bravado, Tony’s health continues to deteriorate.

Knowing his time may be limited, Tony begins putting his affairs in order. He appoints Pepper Potts as CEO of Stark Industries, distancing himself from responsibility. He also hires Natalie Rushman as his assistant, unaware that she is actually undercover S.H.I.E.L.D. agent Natasha Romanoff.

At the Monaco Grand Prix, Tony impulsively enters a race, seeking thrill and distraction. This recklessness places him directly in Ivan Vanko’s trap. Armed with a crude but powerful Arc Reactor and electrified whips, Ivan—now known as Whiplash—attacks the track, tearing apart cars and drawing Tony into the open. With the help of Happy Hogan, Tony deploys his portable Mark V armor and defeats Vanko in a brutal, close-quarters fight. Before being taken into custody, Ivan declares that Tony has made a powerful enemy.

While imprisoned, Ivan is secretly approached by Justin Hammer, who sees an opportunity. Hammer breaks him out and recruits him to build advanced weaponry, hoping to surpass Stark and restore his own reputation. Ivan agrees but has his own agenda: he plans to destroy Tony not just physically, but symbolically.

Meanwhile, Tony’s condition worsens. His erratic behavior culminates in a chaotic birthday party where, intoxicated and wearing the Iron Man suit, he endangers his guests. His close friend, James Rhodes, intervenes using an earlier suit prototype, leading to a destructive clash between the two. Rhodes ultimately confiscates the armor and delivers it to the military, where it is weaponized into the War Machine suit with Hammer’s assistance.

At his lowest point, Tony is confronted by Nick Fury, who reveals Natasha’s true identity and presents Tony with a box of Howard Stark’s old research. Inside, Tony discovers a hidden message: his father believed in him and left behind the key to solving the Arc Reactor problem. Using a 3D model of the original Stark Expo, Tony realizes it encodes the structure of a new, previously unknown element. With the help of J.A.R.V.I.S., he constructs a particle accelerator in his home lab and successfully synthesizes this new element, creating an improved Arc Reactor that cures his poisoning and restores his strength.

At the Stark Expo, Justin Hammer unveils a line of military drones, with Rhodes piloting the heavily armed War Machine armor. However, Ivan Vanko reveals his true plan: he has secretly taken control of all the drones and Rhodes’ suit. The machines turn on the crowd, causing widespread chaos. As Iron Man arrives to intervene, Hammer is arrested, unable to regain control.

At the same time, Natasha Romanoff and Happy Hogan infiltrate Hammer Industries to stop Ivan. Although Ivan has already left, Natasha manages to restore control of Rhodes’ armor, allowing him to rejoin Tony in the fight.

The final battle unfolds at the Expo, where Ivan confronts them in a new, heavily armored suit equipped with enhanced whips. Working together, Tony and Rhodes manage to overpower him. However, in defeat, Ivan activates a failsafe: all drones and his own suit begin to self-destruct. Tony rushes to save Pepper, narrowly escaping the explosions. In the aftermath, Tony and Pepper finally acknowledge their feelings and share a moment of reconciliation.

Later, at a S.H.I.E.L.D. debriefing, Nick Fury informs Tony that he is deemed unsuitable for the Avengers Initiative as a member—but valuable as a consultant. Tony agrees, on the condition that he and Rhodes receive recognition for their actions.

In a final scene, S.H.I.E.L.D. agent Phil Coulson arrives at a remote crater in New Mexico. Reporting to Fury, he reveals the discovery of an object: a mysterious hammer—teasing the arrival of Thor.