Tetsuo: The Iron Man (1989)

A strange man known only as the "metal fetishist", who seems to have an insane compulsion to stick scrap metal into his body, is hit and possibly killed by a Japanese "salaryman", out for a drive with his girlfriend. The salaryman then notices that he is being slowly overtaken by some kind of disease that is turning his body into scrap metal, and that his nemesis is not in fact dead but is somehow masterminding and guiding his rage and frustration-fueled transformation.