The actor revealed that rumours his character Aldrich Killian will be a major part in the film's 'Extremis' storyline are unfounded.
He referred to his roles in Iron Man 3 and Prometheus as "really kind of cameo stuff" in an interview with Vulture.
"Based on the first two movies, there's a great chemistry between Robert [Downey Jr] and Gwyneth [Paltrow], and I just think the films have a fun, joyful sort of quality about them," he said of Iron Man 3. "I've just enjoyed them. So I just felt like I wanted to be a part of this.
"I mean, on some level, it's tricky because you feel like a bit of an outsider. You don't really live the experience that you do when you're there all day every day with everybody.
"But at the same time, it can be more fun sometimes because you're just working in concentrated spurts."
He also addressed his decision to pass up on 20th Century Fox's 2003 Daredevil movie.
"The thing about Daredevil was that it was the role of Daredevil [that I didn't want to do]," he said.
"It was ten years ago. I've probably loosened up, and I feel a little more experimental in what I'll take on these days, but I still don't know that I would want to play the superhero myself, since I'm playing a different kind of character in this film."
Marvel Studios' Iron Man 3 is scheduled for release on April 26, 2013 in the UK and May 3, 2013 in the US.