In the beginning of the film, a man who is the leader of the evil organisation Hydra is looking for a ancient artifact. The opening sequence shows us how he finds it and a bit of why he requires it. The rest of the film is about a scientist wanting to make an American super natural army, Captain America being the first of these super-natural soldiers and the last as Hydra kills the scientist. The rest of the film is about Captain America defeating Hydra.
The opening sequence of this film is something we could consider doing as it is a flash back. Flash backs help explain a situation happening later in the film and we could have used a flash back in the same way for our opening sequence.