There was an issue of Warhammer that had a flexi-disc with a thrash metal track:
"Blood for the Blood God" by Sabbat.
https://www.youtube.com/watch?v=39sAIzrbmk8
Which is best described as "magnificently unlistenable" [0]
I got the flexidisc to play only a couple of times, and mercifully never in the presence of my mother (who was also an RE teacher, though not the one I mention in my other comment)
[0] to repurpose a review quote that was on the shrinkwrap cover of Guns by the British indie-prog-punk-marvel, Cardiacs
40K is, if you ask me, the first hint of the beginning of the end of Warhammer (quite early on). Though I did have a go at the Adeptus Titanicus stuff.
The high point for me was WFRP. I found my 1986 hardback first edition of that the other day.
While one of my secondary school teachers was telling us we were dabbling with the occult, another (a beloved english teacher) enjoyed the imagination of it and wanted to be taught how to play Chaos Marauders so that he wouldn't lose to his nephew.
Electric Wizard, "Dopethrone"
And nowadays we've got stuff like Children of Bodom (RIP Alexi) and others that are pretty in your face.
Monsters from the past would have a stroke if they listened to these bands.
Btw: A thread about metal in HN? I Love it \m/
Pretty much:
This was written by Motley Crue's bass player Nikki Sixx. In the band's biography The Dirt, Tom Zutaut, who signed the band to Elektra Records, explains that Sixx was exploring Satanism at the time, and wanted to call the song (and the album) "Shout With The Devil." Zutaut was having a hard enough time getting the label to promote the band, and he knew the title would make it an even harder sell, but Sixx was determined to go with the devil theme, telling Zutaut: "It just looks cool. It's meaningless symbols and s--t. I'm just doing it to piss people off. It's not like I worship Satan or something."
When Zutaut saw Sixx two nights later, he witnessed a knife and fork rise off the table and stick into the ceiling. Zutaut writes: "I looked at Nikki and freaked out. 'There is no more 'Shout With The Devil.' If you keep shouting with the devil, you're going to get killed.' I truly believe that Nikki had unknowingly tapped into something evil, something more dangerous than he could control that was on the verge of seriously hurting him. Nikki must have realized the same thing, because he decided on his own to change the album title to Shout At The Devil."
There's also an old TV interview that predates their autobiography where they ask Nikki outright if he was a devil worshiper or satanic and he just laughs and tells them "Pssssshhh no! The album is called "Shout AT the Devil" not "Shout WITH the Devil!""
https://www.youtube.com/watch?v=2lvs2FzF64o
Also, some times fantasy themes appeared in metal videos, even if the content of the song had nothing to do with it. I believe the bands or their promoters were just playing into this to piss of the parents (even more).
For example, Mötley Crüe's video for "Looks That Kill":
https://www.youtube.com/watch?v=9wPHxQMgdKs
Mötley Crüe was basically just a party band: more about sex, drugs and rock'n'roll, than about any fantasy nonsense. The song "Shout at the Devil" on the same-named album, and the Satanic imagery and whatnot, was almost certainly likewise just to piss of conservative Christian parents.