Tony Stark (RD) is a genius at weapon designing and the CEO of Stark industries, the biggest and the most advanced in the weapons business. While on a visit to Afghanistan for a live demo he is kidnapped by terrorists and asked to develop missiles. Instead he works on a prototype to design an iron armored suit, using which he escapes.

The incident changes his life. On getting back he announces that Stark industries is getting out of the weapons business. He works further on the suit to take it closer to perfection. His two cornerstones are his friend Rhodey (TH) and Secretary Pepper Potts (GP). Both unaware of his adventures till the very end of the movie. 

For business he trusts Obadiah Stane (JB), his father's friend and partner. But it turns out that he is the man who all this while was trying to get him killed. And he's the person who's been selling weapons to the bad guys. And he has managed to lay his hands on the prototype of the Iron Man suit. As a result, in the end we have a Iron Man (Good and Brainy) vs Iron Man (Bad and Brawny) fight.