This film pretty much follows the story with very few exceptions and possible ending. However the few exceptions and ending is what makes this story work as a movie instead of a long poem. Stories being told may ways have different insights and there should be no conflict between the reader and viewer and both stories are real to the observer.
For you that forgot the story and you that know the story well but have not seen this movie basically we are looking at a story that you may or may not have had an opportunity to sidestep in school but can never have a grasp on social history with out it. Some call it real and lost in antiquity. Others say that Homer had a Good imagination. And others treat it as an allegory with a historical background.
Brad Pitt who has played fickle people before is excellent in the part of Achilles and is sort of a heel. Nothing less was expected. It was the other actors that played their parts so well that you forgot you were watching the movie.
----------------------------------------------------- Two Trojan princes are the guests of the Spartan ruler Menelaus (Brendan Gleeson). While Menelaus is preoccupied with other matters he leaves his wife, Helen of Sparta (Diane Kruger), to her own devises. The younger Trojan prince Paris (Orlando Bloom) is left alone to many times with Helen and decides against everyone else's better judgment to make her Helen of Troy and thus pilfers her from Menelaus.
As a husband Menelaus is of course miffed. However his brother the Greek king Agamemnon (Brian Cox) sees this as an opportunity to absorb Troy into his territory. Natural this spawns a war in which Agamemnon recruits Achilles an extremely gifted and charmed warrior. Achilles goes to make a name for him self. He brings his cronies, and his cousin. Together they do many bold and callous things.
I will not go into the details of the war as you either know or will soon know the details. However I will say that I thought that the Trojan horse was well and realistically designed. And you may want to pay attention to the background music as it is relevant to the film.