Whether or not the Trojan War took place is a debate for another time, but Homer's Iliad and Odyssey tell the story of ancient Greek warfare as a coalition of city-states battling against a common enemy: Troy. The 2004 feature film Troy also purports to tell this story, but it gets a lot wrong when you compare it to the epic poems.
As far as movies about Greek mythology go, Troy presents an exciting version of the storied conflict, but manages to stifle some of the most compelling things about the conflict and its heroic - and not-so-heroic - characters. How real was Troy?
In the traditional telling, the Trojan War begins when Paris, a Trojan prince, takes Helen, wife to King Menelaus of Sparta. Helen and Paris may have eloped, making Menelaus a cuckold, but her husband convinces King Agamemnon of Mycenae (also called Argos) to lead an expedition to bring Helen back to Greece.
Agamemnon, Menelaus's brother, sails a fleet of a thousand ships, according to legend, and great warriors like Achilles and Odysseus accompany him. The ensuing battles and conflicts take place over a decade, collectively known as the Trojan War, and appear in the Iliad and the Odyssey. The movie Troy depicts these events over only two weeks.
In the Iliad, the central conflict isn't between Achilles and the Trojans, but between Agamemnon and Achilles. Just before the Iliad begins, Agamemnon made Chryseis, daughter of a priest to Apollo, his concubine. When Chryseis's father, Chryses, tries to buy his daughter's freedom, Agamemnon refuses.
He finally relents after Apollo punishes his army with disease and death, but only if he can get a new concubine. He decides he wants Trojan princess Briseis, who was Achilles's war-prize wife. Achilles is furious, and while he gives up his bride, he declares he's done fighting for Agamemnon.
Without Achilles, the Greeks suffer great defeats. Achilles's friend Patroclus replaces Achilles on the field of battle, but Apollo again intervenes, this time for the Trojans. Patroclus dies by the hand of Hector, whom Achilles kills in return.
All of this happens in the Iliad, but there is no information about Achilles's fate. Later works, including the Odyssey, allude to his death. The work describes how Achilles, still full of rage, went to Troy to kill Hector's brother, Paris, but perished by an arrow to the heel, his lone vulnerable body part.
Again, Apollo became involved, as the Greek god guided the fatal blow. Regardless, the Odyssey clarifies that by the time the Trojan Horse entered, Achilles was dead.
In the movie, Achilles is in the horse as it goes into Troy. Achilles never lived to see it, much less take a ride in it.
Bronze is an inferior metal to steel and iron, and - as a sword - was particularly fragile. The Iliad does mention iron, but rarely in reference to weapons. Achilles slashes Hector through the neck - a soft, unprotected part of the body - with a bronze blade at the end of a spear.
Troy's sword fights, presumably conducted with bronze weaponry, are unrealistic in the resiliency of the swords, as well as in the number of deaths by gashes. Bronze swords were much more effective at slashing, rather than piercing, especially since the latter could mean damage to the sword itself. A Bronze-Age sword probably couldn't have gone all the way through a human chest, much less through armor.
In the movie Troy, Helen and Paris get word the Greeks are coming to take her back. Paris says they should run away together, but Helen tells Paris she doesn't want him to leave his home for her. He replies she has left her home, but Helen tells him, "Sparta was never my home. My parents sent me there when I was 16 to marry Menelaus, but it was never my home."
This comment is not accurate. Helen is the daughter of Leda, the Queen of Sparta, whom Zeus (in the form of a swan) seduced. Helen, with her beauty and lineage, had many suitors, and her father, King Tyndareus, chose Menelaus as her husband. It was after they married that Menelaus became King of Sparta.