Robert Downey Jr. is set to star in his first big-budget action movie - the comic book adaptation "Iron Man". Jon Favreau is directing the movie, which will be distributed by Paramount Pictures in May 2008 reports the trades.

Downey will portray Tony Stark, a billionaire industrialist and genius inventor who is kidnapped and forced to build a devastating weapon. Using his intelligence and ingenuity, Stark instead builds a high-tech suit of armor and escapes captivity.

Upon his return to the U.S., he uncovers a plot with global implications and must don his armor and protect the world. Principal photography is set to begin in February.