Oystein Aarseth (Norwegian: ['oystein 'os@t]; 22 March 1968 - 10 August 1993), better known by his stage name Euronymous, was a Norwegian guitarist. Euronymous was a founder of and central figure in the early Norwegian black metal scene. He was a co-founder of the Norwegian black metal band Mayhem. He was also founder and owner of the extreme metal record label Deathlike Silence Productions and record shop Helvete.
Black metal and death metal
Euronymous said that the term black metal can apply to any kind of metal, so long as it is "Satanic" and "heavy". He said "If a band cultivates and worships Satan, it's black metal" and that "In a way, it can be ordinary heavy metal or just noise. What's important is that it's Satanic; that's what makes it black metal". He rejected bands like Immortal being called black metal, "as they are not Satanists", but supported the band nonetheless. As noted earlier, bands who had LaVeyan beliefs were also rejected. When it was pointed out that Venom (the band who coined the term 'black metal') only used 'Satanism' as a gimmick, Euronymous said that he and the 'Black Circle' "choose to believe otherwise".  Likewise, Euronymous said that the term death metal can apply to any kind of metal, so long as the band "cultivates and worships death". Euronymous lamented the commercialization and loss of extremity within death metal. He said "Real Death Metal should be something normal people are afraid of, not something mothers can listen to" and "Death Metal is for brutal people who are capable of killing, it's not for idiotic children who want to have [a] funny hobby after school".  Like many others in the black metal scene, Euronymous originally believed that black metal should stay underground. However, he later changed his mind and said the idea should be got rid of. He believed that the idea of staying underground came from hardcore punk and said "Those who scream most about being in 'underground' is also often those who make so bad music that they don't have a chance to get big themselves". He added: "I wouldn't mind making DSP big and earn a million, as long as I don't change my ways of thinking and being [...] If there were one million black metal fans in the world, most of them would be jerks, but there would be really many true and brutal people as well. The bigger we get, the more we can manipulate people into thinking like us".

Q: What is black metal?
A: black metal can apply to any kind of metal, so long as it is "Satanic" and "heavy".

Q: What is death metal?
A: death metal can apply to any kind of metal, so long as the band "cultivates and worships death".

Q: What are some of Euronymous' beliefs about black metal?
A: ". He said "If a band cultivates and worships Satan, it's black metal" and
What were some of Euronymous' beliefs about death metal?
What's important is that it's Satanic; that's what makes it black metal".
What's important is that it's Satanic; that's what makes it black metal".