Day the Earth Stood Still Trailer

from Wikipedia...
The Day the Earth Stood Still is a 1951 science fiction film which tells the story of a humanoid alien who comes to Earth to warn its leaders not to take their conflicts into space, or they will face lethal consequences.
It stars Michael Rennie, Patricia Neal, Hugh Marlowe, Sam Jaffe, Billy Gray, Frances Bavier, and Lock Martin. Supporting cast includes journalist Drew Pearson. The movie was adapted by Edmund H. North from the story "Farewell to the Master" by Harry Bates, and directed by Robert Wise. The score was written by Bernard Herrmann and is notable for its use of a theremin.