Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
This is a fantasy adventure movie that uses characters from ancient Greek myths and magic straight out of fairy tales. The special effects were created by the great Ray Harryhausen, but they seemed a bit outdated in 1981 after Star Wars and Alien and because computer animation was starting to look better on the big screen. But it's still fun if you don't look at it too carefully. It was re-made in 2010.
The story is about Perseus, the half-human son of Zeus, and his quest to save his fiance princess Andromeda and her kingdom from The Kraken, a beast used by Poseidon the God of the Sea when Zeus tells him to. During Perseus' journey he has to fight various monsters and tame a flying horse Pegasus, but his main goal is to cut of the head of Medusa so he can use her eyes to kill the Kraken. According to this movie, Medusa was a beautiful woman who was seduced by Poseidon in Aphrodite's temple, but the Goddess of Love was insulted so she turned Medusa into a hideous monster with the long body of a snake on the bottom, and the top part of a woman with two arms, breasts, scaled skin, a head full of snakes instead of hair, and a huge rattle on the end of her tail. One look into her glowing eyes can turn any living creature into stone. Three blind witches tell Perseus that the only way he can kill the Kraken is to use Medusa to turn it into stone.
Perseus travels to Medusa's temple in the underworld which is full of men who were turned to stone. When he and his men are attacked by a two-headed dog he drops his sword and a python crawls onto it. In a laughable segment which is probably supposed to be tense and fraught with danger, he hesitates, makes faces, then finally grabs the sword and pulls it out from under the poor harmless snake. (Maybe the scene works if you're afraid of snakes.)
Medusa shoots arrows at him, but Perseus watches her reflection in his shield then then he chops off her head and wraps it up in his cloak. He returns home and holds the head to the Kraken to turn it to stone. He frees Andromeda who is chained to the rocks by the sea.
There are various versions of the ancient Greek myths, but this movie completely makes up its own. For example, in the myths Perseus flew using winged sandals he borrowed from Hermes, but in this movie he flies on the winged horse Pegasus. In the myths Pegasus wasn't even born until Perseus killed Medusa and he grew out of her blood. In the myths Andromeda is in danger from a sea serpent, but in the movie it's the Kraken, which is not even a monster out of any of Greek myths. Perseus decapitates the sea monster in the myths and uses Medusa to kill a tyrant king and his followers, not the sea monster. And in the myths Perseus cuts off Medusa's head off while she's sleeping in a cave. He doesn't throw her head in the ocean, he gives it to the goddess Athena. And while I'm ranting here, there aren't even any Titans in this movie! Medusa and the Kraken are not Titans!
Medusa and her snake hair are made out of clay animated special effects, but the snake is a real python.