Captain America has been the leader of The Avengers for a while in the comic book world. In the upcoming movie that will stay true and the film will be seen from his point of view.
EW reports that Whedon is using Cap as the main lens for his film. The Avengers is an ensemble movie so each character will play a large part, but Whedon has some good reasons to use Captain America.
As Whedon says, “So much of [The Avengers] story takes place from Steve Rogers’ perspective, since he’s the guy who just woke up and sees this weird-ass world.” He adds, “Everyone else has been living in it. He’s the guy that feels that sense of loss.”
Coming into the new movie with the established character, Whedon points out that "[Captain America] is kind of the ultimate loner in that way. There is an anachronism to him, and Chris[Evans] and I have always tried to, without making it goofy or too obvious, make him that same grounded ’40s Steve Rogers he was in the other movie.”
Talking about the other characters and their role in the film, Whedon said “You get them in a world, the world of S.H.I.E.L.D., where they fit in. And you say upfront, these are monsters. These are freaks. These are not you and me, and what are they doing here? How are they human beings? Let’s just investigate that.”
