The Morality of Greek Myths

King Dionysius I of Syracuse

My myth was Damon and Pythias, a story of true friendship.  In Syracuse lived two young men, Damon and Pythias, who were the truest friends anyone could have.  The reigning king of Syracuse, Dionysius, was a tyrant, cruel and unjust, and sentences Pythias to death.  Pythias wanted to settle his affairs before death, but was forced to leave someone in his place to ensure his return.  Damon came to take his place, and Pythias went to do what he needed to.  But Pythias was held up by obstacles and was late, so Dionysius prepared Damon's execution.  However, Pythias came just before Damon was killed, and this act of friendship caused Dionysius to revoke the death sentence and ask Pythias and Damon to be his friends.
The moral of the story is to be faithful to your friends and they will be faithful to you, as shown by Damon's initial trust in Pythias that he would return and not leave him to die.  Pythias does remain faithful and comes back to die, saving Damon.  Thus the virtue that is advocated through this myth is loyalty to friends.