Aliens have been invading Earth, at least according to Hollywood, since the early days of cinema.And what audiences most adore about the sub-genre of science fiction is that not only do the aliens come in all shapes, sizes and with varied missions, but oftentimes the alien invasion is a metaphor for something much larger in our society.

read more 15 Best Alien Invasion Movies: Mars Attacks, But Who Else? – Movie Fanatic.