What is the moral of the myth Europa and the bull?
The myth of Europa is the story of how Zeus, king of the gods, kidnaps and seduces Europa. To do this he turns himself into a tame white bull to encourage her to come close. She pets him, then climbs on, whereupon he runs into the sea and carries her off to the island of Crete, where she becomes the first queen.
When we think of "myth," it is best to consider it as a story which conveys certain cultural values. It may or may not be literally "true." In this story, if we were from Crete, we'd have a story about the origin of our civilization that rests with Zeus, king of the gods. Similarly, it's a reminder that the center of the world used to be in what we now consider the Mdidle East. The ancient civilizations there were once relatively advanced, and were where agriculture first developed. The story indicates that civilization spread westward to Europe from there.
For most myths, though, the meaning isn't at once obvious. It is something to contemplate. It seems more reasonable to take away a lesson along the lines of "don't get carried away." If there's a lesson in Europa's kidnapping, it seems likely that it involves being aware.