The adaptaters of The Lord of the Rings put a lot of effort to include everyone's favourite bits from the book. How well does the movie Troy do by this criterion?
First off, let me try to remember the story of the Trojan War.
(The following is not a spoiler for the movie. But the fact that it is not a spoiler is itself a spoiler.)
It all starts with Eris's not being invited to a feast of the gods, in revenge for which she throws the golden apple inscribed 'To the fairest' onto the table. Argument breaks out amongst the goddesses present, and in the end to make peace they agree to appoint a mortal man as judge.
They choose Paris, a prince of Troy then living incognito as a shepherd. Apart from parading in front of him unclothed, the goddesses also attempt to bribe him. Athena, for example, offers wisdom and unbeatable prowess in battle. Paris chooses Aphrodite, goddess of love. What did she offer him? The most beautiful mortal woman in the world as his bride.
So it is that Paris abducts Helen, child-wife of King Meneleus (she is given no choice in the matter) and takes her to Troy.
The Greek city-states band together under Agamemnon to form a war party to retrieve her. Before setting out they naturally consult the oracle of Delphi and receive the usual cryptic advice. One of the kings ends up sacrificing his daughter to ensure victory; Agamemnon is assured that he cannot prevail without the famous young warrior Achilles. He sends the wily king Odysseus to fetch him.
Achilles's mother is a sea nymph, and when he was a baby she dipped him in the Rive Styx, giving him invulnerable skin (apart from the spot on his ankle where she held on to him). Despite this, she has had a premonition that he will die if he goes to war. She persuades him to hide himself and his best friend Petrocles amongst the princesses of the court disguised as a girl (he is a very young warrior). To flush him out, Odysseus disguises himself as a peddler so he can visit the princesses, and includes a sword amongst the ribbons and trinkets he shows them. He persuades the boy to accompany them with stories of glory in battle.
More adventures ensue but eventually they arrive at Troy. The affair with the golden apple has left the gods divided as to which side they support. As a result, after the initial skirmishes, neither side has won, and as weeks and months pass they settle in to a long, drawn-out siege. There is stuff with heroes like Ajax here, but I don't know this bit. Achilles grows from a boy in to a ferocious bully, almost as dangerous to his friends as his foes.
Ten years pass. Things look bad for the Greeks: morale is low, and Achilles is sulking in his tent after an argument over ownership of a captive. His lover Petrocles goes to battle dressed in Achilles's distinctive shiny gold armour, partly to rally the Greeks, partly to shame Achilles in to rejoining himself. Paris's brother Hector kills Petrocles. When Achilles is told of Petrocles's death, he goes in to a frenzy of grief, killing the messenger out of hand.
Achilles fights Hector cheered on by the Greek hordes. Hector is wearing Achilles's golden armour, looted from Petrocles's corpse. Achilles kills Hector, and then drags his body through the dust around the city three times. In a society where warring tribes routinely exchange prisoners and allow for the honourable burial of fallen foes, this is an unforgivable war crime.
Paris gets his revenge by ambushing Achilles while he is out hunting. He shoots him with a poisoned arrow (not really a very heroic act); guided by Aphrodite, he hits Achilles in his sole weak spot, the ankle. Achilles dies of the poison.
In the end, desperate to finish the war, the Greeks resort to the famous Trojan horse gambit. The Trojans assume the horse is an offering to the sea god Poseidon (it is one of his sacred animals), and by taking it in the city they will bring the Greeks back luck on the voyage home. The sole dissenting voice is Cassandra, a prophetess cursed by Apollo to always predict truly, and to never be believed. That night the Greeks emerge from the horse and sack the city, killing everyone in an orgy of violence. King Priam in despair leaps to his death from the highest tower of the city.
Using a votive offering (the horse) in this way is clever but also dishonourable -- and the Greeks are cursed by the gods for it. Odysseus notoriously spends ten years struggling to get home through Poseidon's wrath. Agamemnon arrives home just in time to be killed by his wife. Meneleus and Helen, however, do live happily ever after.
... but none of the above happens in the movie.
Well, I tell a lie. The battle between Hector and Achilles is still in, though oddly the Greek army did not bother to watch, and the bit with the horse could not really have been left out.
It was probably a bad sign that the very first notes of the opening titles had me laughing out loud.