In a closely guarded lab, Anthony "Tony" Stark shows off a new invention to US military defense officials. He has developed micro-transistors capable of powering up things such as magnets; turning them into powerful weapons strong enough to pull open a thick metal door from a distance. They increase magnetic force a thousandfold! Stark impresses the military brass with his new inventions, while at the same time impressing the ladies of the international jet set with his dashing good looks and incredible personal wealth.
Across the globe, the evil Red tyrant Wong-Chu takes over another small village in Vietnam, defeating its strongest men in contests of judo. Meanwhile, Tony Stark has arrived in Vietnam to observe the testing micro-transistor-powered weaponry, which allow heavy items like mortars to be reduced in size no larger or heavier than a flashlight. Accompanying a squad of soldiers equipped with his weaponry on a patrol through the jungle, he accidentally triggers a tripwire that detonates a landmine. The wounded Stark is captured by Wong-Chu's forces and taken to their nearby headquarters. Wong-Chu realizes his prisoner is a "famous Yankee inventor" and decides that he will put him to work in service of the Communist insurgency even though doctors determine the young inventor only has days to live before "shrapnel reaches his heart."
Wong-Chu falsely promises that he will have a surgeon save Stark's life if he will agree to develop new high-tech weapons for him. Even though he saw through Wong-Chu's words to his true intentions, to make him work until his death, Stark agrees, in order to try and save his own life with his technical abilities and Wong-Chu's resources. Given access to scrap metal and tools, Stark promises he will deliver a "fantastic weapon," but sets out in building a mechanism that will help stop the shrapnel from penetrating his heart. He is given an assistant named Professor Yinsen, a famous physicist whom Stark had read about while in college. Working together, the two finalize work on Stark's project: an iron body suit with a chest plate that will keep the shrapnel at bay through use of transistor-powered magnets.
Just as Stark has donned the life-saving suit and begun to power it with electrical current from a generator, Wong-Chu attempts to come check on his prisoners. Professor Yinsen rushes out into the hallway shouting at Wong-Chu and is shot dead by armed guards, buying the precious seconds Stark needed to fully charge the armor. Tony Stark, as Iron Man, hears the murder of his friend and swears he will avenge his death. He tries to rise and steady himself in the Iron Man armor, but discovers it is like learning to walk again. He quickly gets the hang of operating the armor and evades detection from Wong-Chu by leaping to the ceiling and holding himself there using suction cups. After Wong-Chu leaves the room, the tyrant heads outside to "amuse himself" with his favorite sport, challenging the villagers to a duel of judo.
Iron Man descends from the ceiling and finds a coat and hat, with which to cover his armor, and wanders outside to find Wong-Chu tossing people around in the judo arena. Iron Man challenges Wong-Chu, then takes off his coat and hat to reveal the shocking visage of Iron Man! The metal monster walks up to Wong-Chu, picks him up, and twirls him around before tossing him into the brush. Wong-Chu demands that his guards open fire on Iron Man, but the bullets just bounce off the armored figure's metal chest plate. Iron Man then uses "reverse magnetism" to repel the enemy weapons. Wong-Chu tries to get to the speakers of the nearest building, in order to put a bounty on Iron Man, but Stark manages to create electrical interference and switch the radio's channel, telling Wong-Chu's troops through the speaker to flee their leader before the Iron Man "slays [them] all." Iron Man cuts down the building's door using a transistor-powered buzz-saw, but as soon as he enters the Communist menace fells him with a file cabinet loaded with rocks.
Wong-Chu escapes to order the execution of all his prisoners, but Iron Man, low on energy and too weak to continue pursuit, uses his armor's lubrication system to launch a stream of oil towards an ammunition depot near the fleeing Wong-Chu. He then sets fire to the oil stream using a miniature torch in one of the armor's gauntlets, causing the ammo dump to explode, and seemingly killing Wong-Chu. His batteries now recharged, Iron Man dons his coat and hat and walks away into the jungle.

A billionaire industrialist and genius inventor, Tony Stark (Robert Downey Jr.), is conducting weapons tests overseas, but terrorists kidnap him to force him to build a devastating weapon. Instead, he builds an armored suit and upends his captors. Returning to America, Stark refines the suit and uses it to combat crime and terrorism.

With the world now aware that he is Iron Man, billionaire inventor Tony Stark (Robert Downey Jr.) faces pressure from all sides to share his technology with the military. He is reluctant to divulge the secrets of his armored suit, fearing the information will fall into the wrong hands. With Pepper Potts (Gwyneth Paltrow) and "Rhodey" Rhodes (Don Cheadle) by his side, Tony must forge new alliances and confront a powerful new enemy.

When Thor's evil brother, Loki (Tom Hiddleston), gains access to the unlimited power of the energy cube called the Tesseract, Nick Fury (Samuel L. Jackson), director of S.H.I.E.L.D., initiates a superhero recruitment effort to defeat the unprecedented threat to Earth. Joining Fury's "dream team" are Iron Man (Robert Downey Jr.), Captain America (Chris Evans), the Hulk (Mark Ruffalo), Thor (Chris Hemsworth), the Black Widow (Scarlett Johansson) and Hawkeye (Jeremy Renner).

Plagued with worry and insomnia since saving New York from destruction, Tony Stark (Robert Downey Jr.), now, is more dependent on the suits that give him his Iron Man persona -- so much so that every aspect of his life is affected, including his relationship with Pepper (Gwyneth Paltrow). After a malevolent enemy known as the Mandarin (Ben Kingsley) reduces his personal world to rubble, Tony must rely solely on instinct and ingenuity to avenge his losses and protect the people he loves.

When Tony Stark (Robert Downey Jr.) jump-starts a dormant peacekeeping program, things go terribly awry, forcing him, Thor (Chris Hemsworth), the Incredible Hulk (Mark Ruffalo) and the rest of the Avengers to reassemble. As the fate of Earth hangs in the balance, the team is put to the ultimate test as they battle Ultron, a technological terror hell-bent on human extinction. Along the way, they encounter two mysterious and powerful newcomers, Pietro and Wanda Maximoff.