In the story, a New York police officer, James Edwards, is persuaded to join a very secret organisation known as Men In Black. The name comes from the black clothes they wear. He is given the new name Agent J and works with Agent K. The organisation is intended to monitor the many alien beings that live on Earth - mainly in New York - disguised as normal humans.
One day, a flying saucer crashes into Earth. The 'Bug' that it contains is a powerful alien that takes the body of a human. It is searching for an energy source called "The Galaxy". Agents J and K must stop the bug before it can escape. This they manage to do. At the end of the film, Agent K decides that he doesn't want to do this work anymore, and is treated by Agent J so that he won't remember the work he used to do
The movie made over $500 million worldwide in total.
It was followed by sequels Men in Black II and Men in Black 3.
Men in Black (movie) Facts for Kids. Kiddle Encyclopedia.