Any Sci-Fi fanatic here that might know what movie i am looking for?

is there some one in here that is a scifi fan (like alien invasion movies etc.)? i am searching since around 2 month for a movie i once watched and i would like to watch it again, but i dont know the titel. I only know that the aliens can control the mind of people AND there was one scene on top of a building where the alien explained the humans where planted on earth to erase all threats for the aliens when they arrive. There where 2 aliens, a good one and a bad one. Absolutely no clue anymore what the movie name was.