All of the mighty gods were invited to the wedding of Peleus and Thetis, all but the goddess Eris.
Everyone else has given a gift. Why should I not do the same?
Eris, goddess of strife and arguing, took out a golden apple and dropped it through the heavens into the wedding party. When Peleus went to pick it up, the room fell silent and still. On the apple said:"A golden apple, another gift to us. Upon it reads, too the fairest. I must give the apple to the to the most beautiful of you all. Athena, Hera, and Aphrodite stepped forward, but Zeus took the apple and gave it to Hermes to take to the sheered Paris.
Again, each goddess appeared for the apple. Aphrodite was wearing her belt of love and desire. So the goddess' took of their clothes and each promised Paris wonderful things. Paris gave the apple to Aphrodite in the end, receiving the most beautiful women in Greece.
When Paris came back, his father, King Priam, said that he was at the time of choosing a wife. Paris immediately answered with the name Helen. So he went to Troy to send a message from Priam to Sparta. King Menelaus, warmly greeted him, but when he was called away on urgent business, He told Helen to entertain Paris. So when they were alone, Aphrodite let loose another arrow, and Helen fell in love with Paris.
Helen and Paris stole what they could from Menelaus, and ran across Sparta and set sail across the Aegean sea. When Menelaus found out, he ran to his brother, high king of all Greeks. They sent envoys to to Troy demanding Helen. But Priam had no knowledge of Helen, but said that his son would have done what he did for a reason and Priam would defend his decision no matter the cost. The high king sent for Odysseus, and readied his and other kings' armies to attack.
Helen and Paris finally arrived at Troy once again, and every man fell in love with her and every woman enchanted by her beauty. King Priam solemnly swore that no one would ever take Helen away.