Billionaire industrialist Tony Stark, having revealed his identity as the armored superhero, is now under pressure from the government, the press, and the public to share his technology with the military. Unwilling to divulge the secrets of his Iron Man armor, fearing the information will slip into the wrong hands, Stark is adamant about keeping his invention to himself. Meanwhile, his own health is in peril due to the palladium core in his chest—a core that powers the Iron Man suit but is also slowly poisoning him. Amidst this, Stark faces a new and formidable adversary who harbors a personal vendetta against the Stark family.

The malevolent force is Ivan Vanko, son of a Russian physicist who once collaborated with Tony's father, Howard Stark. Vanko blames the Stark family for his own family's misfortunes and seeks retribution. He constructs his own weaponized suit and attacks Stark at a high-profile racing event. Stark survives the assault with the help of his new portable Iron Man suit. The attack forces Stark to reevaluate his mortality and legacy. Stark's strained friendships and professional relationships are tested as he navigates the mounting pressure and his declining health, with his assistant, Pepper Potts, and his friend Lt. Col. James "Rhodey" Rhodes at the center of his tumultuous life.