Iron Man

Tony Stark — genius, arms manufacturer, heir to Stark Industries — is ambushed in Afghanistan by terrorists armed with his own weapons. Shrapnel lodges near his heart. A fellow captive, Ho Yinsen, builds an electromagnet to keep it out; Stark builds a miniaturised arc reactor, then a suit of armour, and escapes. Yinsen dies covering him.

Stark shuts down weapons manufacturing. His business partner and father's old colleague Obadiah Stane — who arranged the ambush — tries to kill him for it. Stark wins.

Then he does the thing that starts everything: at a press conference, instead of reading the cover story, he says "I am Iron Man." No secret identity. The modern superhero era begins with a public admission.

Post-credits: Nick Fury appears in Stark's living room. "You've become part of a bigger universe. You just don't know it yet."

Obadiah Stane had been running weapons to the Ten Rings for years and paid them to kill Stark; they decided a live Stark building them a missile was worth more. What Stark actually builds in the cave, with Ho Yinsen, is the first arc reactor and the Mark I — and the film's turn is that Yinsen chooses to die buying him the sixty seconds it needs to charge.

Stane's own attempt to copy the technology fails on exactly the point Stark solved in a cave: he can build the suit but not miniaturise the reactor, so he takes Stark's out of his chest. Pepper Potts overloads the arc reactor in the Stark Industries roof to stop him.