THE DAY THE EARTH STOOD STILL (1951 Sci Fi Movie)

An Alien and a robot land on Earth and tell mankind that they must stop all aggressive moves toward each other and in the exploration of space with nuclear power. The consequence of non compliance is the total destruction of Earth.

A Classic Science Fiction movie from Robert Wise..
Source: https://archive.org/details/thedaytheearthstoodstill1951_201912