I hope that asking if Metropolis is a Superman movie is a joke. If it is not, I fear we are going to lose great movies to a lack of interest since even intelligent people have not heard of the classics. Metropolis is one of the first and one of the great science fiction films. It was made in 1928 and is silent, but don't let that deter you from trying to find it. Great science fiction did not begin with Star Wars.
By the way, you all were talking about the Hayes code. The Hayes Code was basically the rating system with more bite. Between 1930's-1960's, you had to submit your script for approval to the censors. They would not allow cursing, suggestions of sex, violence, drugs, or anti-religious statements. They had bite for a while until some directors like Otto Preminger were willing to release movies without their approval. People would line up to see what they thought was going to be dirty, but found there was a whole lot more talk about sex than action. By the mid-60's, they had to stop with the Hayes Code and started the ratings system, which led to a lot more freedom in the movies.