This is Greek myth, so unsurprisingly there's the good and the not so good. Gods are needy, jealous, vain, and selfish. Men have the potential to be noble, to live and die for each other, and to love each other. Perseus is both god and man, so he has both positive and negative qualities. Overall, the movie tries to give a positive message.
Mid-level fantasy violence with lots of fighting -- including decapitation, dismemberment, and electrocution, knives, bows and arrows, swords (and sometimes biting). Most of the monsters and creatures, ranging from the giant scorpions and the huge toothy Kraken to the eyeless witches and the slithery Medusa, are pretty scary. We see some blood and charred bodies, as well as some goopy monster guts.
In one scene, Zeus climbs in bed with a mortal woman; it is suggested that they conceive a child, though hardly anything is shown. In another scene, Io tries to demonstrate to Perseus the dangers of Medusa. She attacks him from various angles and eventually lands on top of him, where they linger for a moment, touching hands and gazing into each other's eyes. Another character enters the scene and is embarrassed to find them in that position. Io wears a sexy outfit throughout, including boots and a short skirt. There is no kissing. The computer-generated Medusa is also designed to be slightly sexy.
We hear one use each of "bastard" and "bitch," plus "damn" and "hell." at least once. It should be noted that the words "gods" and "Hades" are used frequently, but only as terms of Greek mythology.
Background characters drink wine at a celebration early in the film.