The currently available Metropolis reconstruction is pretty exhaustive, but if you want to get really detail-intensive you could compare the DVD (which is based on the European print) with a U.S. public-domain release. In order to provide a first-generation negative for stateside distribution, much of the action was shot twice, resulting in alternate negatives-- note the variation in Brigitte Helm's performance on "Let the machines stop!" for starters.

Also, Thea von Harbou's novelization is available in a decent English translation. It's worth hunting down.