There's almost something of a Tetsuo the Iron Man Cinematic Universe (TIMCU), because first there was this short film, The Phantom of Regular Size, which then gave way to the slightly longer (but still short film) The Adventures of Electric Rod Boy (1987), and then finally, in 1988, there was the feature-length Tetsuo the Iron Man. Then, that film received two sequels, so anyone who wants to catch up on the whole series within a short period of time is going to absolutely melt their brain. It's all metallic body horror, dizzying editing, gross-out special effects, and loud clanging noises.
That 1988 film is still the best of the bunch, but watching the shorts as proof-of-concept movies for it can be interesting. This one, The Phantom of Regular Size, isn't as good as Adventures of Electric Rod Boy, and I wish I'd watched it first, but there's still a twisted charm to this extra-short short, and the music and sound effects are as good as ever.