Not much is known about the story of Iron Man 3. They are keeping it under the wraps. But then it is Internet and little bits of leaks here and there is enough to make a story. So whatever leaked information we have the story of Iron Man could be like this which is also probable to great extend.
The second half of the plot is based in China. Iron Man goes to China to save his friend’s daughter who has been kidnapped by Mandrain played by Ben Kingsley. Andy Lau is playing the role of Tony Stark’s friend.
So what is first half of the movie all about. So far we know that Hansen and Killian are developing the Extremis serum, and we speculate that Mandarin will likely get his (or its) hands on it, wreaking some havoc on Iron Man. With their Extremis serum, Hansen and Killian trying to create super soldiers.
So this is in tidbit the story of Iron Man 3. The movie will reportedly see Iron Man fly over the Great Wall of China, the National Palace Museum and various landmarks in Shanghai.