"Iron Man 3," which opens in most of the world this Friday and on May 3 in the United States, has Downey reprising his role of superhero industrialist Tony Stark from the first two films as well as last summer's "The Avengers."
Collectively, the three films have made about $2.7 billion at the global box office in the past five years.
"Iron Man 3," which continues Stark's storyline from both sets of Marvel franchises, centers around the evil extremist known as The Mandarin (Ben Kingsley) who is hell-bent on destroying the United States.
When The Mandarin destroys Stark's personal world as well as his superhero suit, Stark must begin from scratch, rebuilding his suit, freeing the woman he loves and saving the country from destruction.
Bombs go off in crowds of people and buildings are destroyed in the film that the cast says reflects real-life threats.
"We do live in an unsafe world, that's the truth," Gwyneth Paltrow, who plays Downey's love interest Pepper Potts, told reporters at a news conference this week.
"I don't think there is anything wrong with presenting that idea. We can't lie to our children and pretend the world is perfect."
Marvel's first self-financed film, 2008's "Iron Man," became a global phenomenon, transformed Downey into a superstar and set off a chain of action movies that spawned other franchises, culminating in last year's crossover film, "The Avengers."