Contrary to earlier rumors, it seems that when The First Avenger: Captain America hits the screen, the Star-Spangled Avenger will not be played by Matthew McConaughey. Our friends at IESB.net spoke to Marvel Entertainment executive Kevin Feige, who also confirmed that the film will be a period piece, set during World War II.
Feige says that the film will be an origin piece, detailing how underweight Steve Rogers becomes America's super-soldier, in order to help America fight against the Axis powers. Feige says that, much like Iron Man, the film will be very faithful to the comics.
It was also confirmed that while Captain America's famous shield is seen briefly in Tony Stark's lab in Iron Man, the presence of the shield is just an Easter Egg for the fans - not an actual part of the story of either film.
Finally, Feige says that rumors of Matthew McConaughey playing Captain America are just that - rumors, and are completely false.