Sometimes I even feel that knowing the lyrics can distract from the song, I think this comes down to the discussion between the "program music" and "pure music" proponents. Personally, if we're talking most genres I care most about the vibe I get from a song - even if that deviates from what the artist envisioned. The only notable exception to this being rap because the lyrics are at the forefront. That doesn't mean these things never "touch", it just depends. Clutch for example is a band where the vibe I get from the song is almost always related to the lyrics (granted, Clutch has super tight musicianship and pretty good lyrics). But Metal specifically is also a different beast. Metal - similar to Punk - was borne out of something of a rebellion, being extreme and having a lot of shock value. As I have noted before, I listen to a lot of other music (including some that you could dub "pop" or "with pop sensibilities" and I honestly don't mind pop music as a phenomenon - people can like whatever they want as long as they're not pushy about the music they like) but with different moods/atmospheres in mind. I don't think anyone listens to death metal expecting a philosophical dissertation. Although in the meantime there have been quite a few bands that have gone far and beyond the stereotypes.