For me metal is first of all about the spirit.
It's hard to actually define what "metal-spirit" is. You may say it has to be dark, others may say it's about death, voilence, demons and gods (light 'n happy stuff...) - but in the end you'll never find any particular area, issue, mood or attitude which can fit every one of the undisputed classic metal bands.
When trying to think of a definition for metal, I think the only common base you can come up with for all sub-genres categorized together under the name METAL is history. The sound of metal has evolved for more than three decades, pushed forward by thousands of bands; naturally, the whole process was led by a relatively small group of popular and semi-popular bands (like Led Zeppelin, Deep Purple, Black Sabbath, Judas Priest, Metallica, Death, etc.), but the other bands' part in preserving and developnig this unique sound is great too. Every metal band has been inspired - directly or indirectly - by these leading bands. Usually - but not necessarily - this influence is easily detected when listening - you can smell (hear) it from miles away. A metal band's abition, usually, is to continue "practicing this tradition" in some way or another.
Next time on our show: metal churches and monasteries, priests and monks.
Originally posted by bleed for me
this is sort of wondering from the topic but what i'm trying to say is that when you say extreme, think of both sides of the musical spectrum
Music in general is all about contrasts: creating tension and leading to climax, and then letting it go and calming down for a while. In metal you often have fast shifts of that kind. What goes up to the highest must go down to the lowest in order to keep it well-balanced. Opeth's music, for example, is beautifully balanced.