The Day the Earth Stood Still is a 1951 science fiction film which tells the story of a humanoid spaceman who comes to Earth to convince its leaders to learn how to live in peace.
The film has been selected for preservation in the United States National Film Registry. In spite of the undeniable cliches of the movie (a race of killer robots, a spaceman in a silver suit and a flying saucer etc.), its message of peace and dark outlook regarding human society separates it from the fray of 1950s science fiction and has made it a classic. Filmed in black & white with minimal, but effective special effects, the movie is a model of brisk, economical storytelling and direction.
Of course, Ringo Starr paid tribute to The Day the Earth Stood Still on the cover of one of his better solo albums, Goodnight Vienna (1974).