This movie is AWESOME. It is heralded as the most influential silent film of all time, and I must agree with that sentiment. You sense echos of this film in all of the work that repeats itself over and over again in science fiction works that appear later.
The key for the theme of the movie is, "The Heart Must Be a Mediator Between the Head and the Hands," addressing the growing class gaps that existed in Germany at the time between the intellectual elite and the mass workers in general. Germany at the time was deep in debt with war reparations that had been imposed by Allied leaders at the insistence of their hawkish factions. This film does what many great movies do which is externalize a problem on a 'future society' for a problem that exists contemporaneously in order to make it less controversial and also to make a point.
And there are several points to be made here. The biggest is the folly of the masses turning against the machines from which they sustain life. We need machines, or we will die. There might be some folks who argue to the contrary...I'm not arguing with them because I don't see the point. The second theme/point shown is in the danger of dehumanization. When the workers do it, they endanger the lives of their children. When the elite does it, he endangers the life of his own son. Another theme is a bit of femininity in the value of the woman seen and who is a human and a peace maker vs the value of a machine who isn't even recognized by most for being a monster. The more interesting aspect of all this to me is the passion play element that interjects death, the seven deadly sins and the whore of Babylon into what is otherwise 'hard' science fiction, but that's kind of the point. This is more social science fiction along the lines of Philip K. Dick or Ray Bradbury than Asimov.
The fact that it manages to do all that and have a complex plot with many complex characters and be a SILENT MOVIE is just stunning. The production values would be comparable to something one might see at Sundance today, and the pioneering work on the robot/machine man can compare to all but the highest budget block buster picture today. The impressive set work and models made this futuristic city come to life. The costumes, the acting (non verbal) and even the sign cues were just extremely impressive.
Having said that, the story would have made a lot less sense without the found footage that the early censors had foolishly cut. The whole story made much more sense this way, and I remember being impressed with it the first time around that I saw it. It is definitely the most impressive silent film I've ever seen, passing even the works of Chaplin or Nosfaratu. I enjoyed it, and I think any modern audience really would if you are of an artistic mind set.
I cannot recommend seeing this enough. Even if you don't like it, its worth the effort to see one of the greatest cinematic works all time, and if you do like it, you'll be glad you saw it!