Action film is a film genre where one or more heroes is thrust into a series of challenges that require physical feats, extended fights and frenetic chases. The storyline and character developments are generally not as important as other features that make an action film what it is as explosion, fighting, gun battles and high octane car chases usually come first.
A general action film, consists of a hero(s) and a problem for them to solve and then everyone lives happily ever after but these conventions have been challenged by the likes of arguably one of the best directors in the world like Micheal Bay e.g. Armageddon, When an asteroid the size of Texas is headed for Earth the world's best deep core drilling team is sent to nuke the rock from the inside, but at the end of this film Bruce Willis sacrifices himself to save the world, which shows that even though he was a hero and solves the problem not everyone lives happily ever after as others suffer the consequences from his decision e.g. daughter.
One of the best action films out this year (2010) was Expendables:
This trailer is of Expendables, a very action packed film. It starts off with a narration with a very deep manly voice and then contrasts with explosion and gun fights. It contains many action hero e.g. Jet Li, Jason Statham.
It starts off with gun fights, fist fights and explosion etc, and also finishes the film the same way. You don't really get the story line within the trailer, but there are flashes on the screen giving the audience of an idea what this film is going to be about, as it says it was a job that no one wanted and in doing so they will change history, so it makes the audience expect an action packed film and makes us almost forget about other features that make film, e.g. storyline, which is a common problem with action films.