*Credit to Kobester* Iron Man 3 is Tony Stark's search for the answer to Captain America's question back in The Avengers: "Big man in a suit of armor. Take that away -- what are you?" Tony had been holding onto his arc reactor chest piece because he thought it defined who he was. In the end of IM3, with the help of the Extremis formula, Tony could finally let his arc reactor go because he finally understood that Iron Man is the man who "built" the armor (The Mechanic) and not the armor that wears the man. That similar meaning is also conveyed between Aldrich Killian and the real meaning behind The Mandarin. Killian was Tony, while The Mandarin was just his suit of armor. "I am the Mandarin" was what Killian said to Tony during their final battle, which reverberated the last thing Tony said before the end. Because despite that Tony no longer has any Iron Man suits to wear, it didn't matter anymore because like Tony said in the end of the film even without the armor, "I... AM Iron Man". P.S. On a sidenote, Killian was the human version of The Mandarin's Fing Fang Foom complete with fire breath!