Are aliens scary? Why did they come to earth? What do they want to do?

Aliens must exist. They just haven't been discovered yet. They live on other planets that we call aliens. In fact, they may be scary or friendly, because their ideas should be different from those of the earth. So it's hard to say that their earliest purpose in coming to earth was actually to verify the existence of aliens like us in their eyes. No one can answer what happened later. In fact, aliens are also people. They will also be enlightened, but they will definitely be demonized in movies.