I heard about this movie reading a comic book magazine in elementary school. It piqued my interest and I searched for it on video for rental for several months before finding it. Also included on the video was a short film entitled "Drum struck" which didn't interest me at all. The real meat was Tetsuo.
The "plot" of this film revolves around a businessman (who apparently like to have sex with his girlfriend in public places and film it) who is involved in a hit and run auto accident with a metal fetishist. Soon the man appears to be hallucinating about people sprouting metal appendages until it begins to happen to him. Chunks of scrap metal grow like cancerous tumors. Soon, they're not random scraps but working appliances such as drills. If this isn't bad enough he soon finds out the man he hit (played by the director of the film) is in fact alive and rather peeved.
Absolutely insane violence permeates the film which retains its punch through the black and white film.
The review I read about this film compared it to Eraserhead (A film I still have not seen) which I believe says a lot about Eraserhead. To compare it to a film I've seen I'd say it reminds me of "Un Chien Andalou" with about three more lines of dialog and a lot more gore and violence.
I also recommend the sequel Tetsuo II: Body Hammer. It's similar but bigger. Color, dialog, etc.
10/10