The 47-year-old insisted that the third instalment in the Marvel Studios series will not be predictable.
"These things tend to, in Act 3, really become about the same old things," Downey Jr told Entertainment Weekly.
"So let's really flip that," he continued. "I feel like I don't know where you go after Iron Man 3. Leave it all on the field, you know?"
The first concept art from Iron Man 3 was released earlier this week. It features Tony Stark (Downey Jr) surrounded by armed men and wearing only part of his Iron Man suit.
Iron Man 3 is currently shooting in North Carolina and stars Gwyneth Paltrow, Guy Pearce and Ben Kingsley. It will open in theaters on May 3, 2013.
Watch a trailer for Iron Man 2 below: