Metropolis (1927) talks about the importance of a mediator between the hand and the head. In the movie the head is the capitalists and the hand is the workers. A core aspect of Social Democracy and the Nordic model in Scandinavian countries is the importance of dialogue between trade unions and employees organizations, a mediator of sorts. So does Metropolis advocate for Social Democracy? Metropolis Restored
No, not particularly regarding a mediator. A mediator between the working class and the capital is not an exclusive feature of social democracy and the scandinavian model is a sub category of social democracy. There's rather a strong reference to Marx regarding the revolte. The movie is rather slightly adovcating left-winged politics in general. He might have been favoring social democracy over marxism regarding the outcome of the revolte. This might have been an indirect comment on Marx.