Aliens

I know it's a James Cameron film with Susan Sarandon.  Wait, she's not in it?  Oh, right Sigourney Weaver , I get those two confused.  Signourney is the main character.  The aliens come to the town and it's really scary.  They are not good aliens like E.T., but they're bad aliens.  Is that enough?  I don't know anything about this movie.  I don't even know if that's true.