I've saw these various ones on youtube.
666 at Calling Death (1993)
Black metal and death metal documentary. Interviews with: Deicide, Atrocity, Death, Samael, Impaled Nazarene, Sepultura, Benediction, Cannibal Corpse, Pungent Stench, Paradise Lost, Morbid Angel, Morgoth, Gorefest, Fear Factory, Cathedral, Ancient Rites, Carcass, Messiah, Blasphemy, Immortal, Grave, Unleashed, Tiamat, Iron Curtain, Scott Burns. Spoken language: English, German (English subtitles)
Death Metal - A Documentary (2003)
Death metal documentary made by Bill Zebub from Grimoire Magazine. Interviews with: Peter Steele (Carnivore, Type O Negative), Malignancy, Brutal Truth, Immolation, Mortician, Suffocation, Amon Amarth, James Murphy (Disincarnate, ex-Death, ex-Obituary), Tzefa, Seance, God Dethroned, Cronos (Venom), George Corpsegrinder (Cannibal Corpse). Spoken language: English.
MuchMusic Death Metal Special (1993)
Death Metal special broadcasted by MuchMusic (Canadian TV). Features interviews with Slayer, Sepultura, Cannibal Corpse, Morbid Angel, Gorguts, Atheist, Demolition Hammer, Scott Burns (producer), Entombed, Chuck Schuldiner (Death), Andy LaRocque (King Diamond, ex-Death). Spoken language: English.
MusikByran Thrash Metal Documentary (200?)
Documentary about the history of thrash metal. Broadcasted on SVT2 (Swedish TV). Features interviews with Anthrax, Metallica, Motorhead, Sepultura, Kreator. Spoken languages: English interviews (Swedish subtitles), Swedish commentator (sorry, no English subtitles).
The info was taken from this blog it lists a lot more documentaries.
http://ghostradio-archive.blogspot.com/ ... ocumentary
There is another one I've saw about nwobhm it seems to have been on british television about nwobhm fans going to "heavy metal discos" and playing cardboard guitars along with the music.
I've saw plenty of the other bad ones mentioned here so far but those 4 are my favorites so far.