With all the billions and billions of stars in the universe, each with their own solar systems, it only stands to reason that some planet out there (probably more than one) that has the right conditions for supporting life. According to the odds, we can’t be the only planet with intelligent life forms on it. There have to be others.
The movies portray other life forms as violent and dangerous, but I think this is just a function of Hollywood portraying life as we know it as violent and dangerous. Interterrestrial life that could reach Earth would probably a lot smarter than we are and also have evolved into less violent and dangerous creatures. They would probably be much more peaceful and intelligent than we are and would mean up no harm. If they had the ability to reach Earth, they are obviously more advanced than we are. So I think we have nothing to fear from alien life forms should they visit Earth. Hollywood has just modeled aliens on human behavior and it is faulty to assume that alien life forms would be as uncivilized as we are.