Whenever I listen to it I almost always conclude I like metal better without the singing (my recurring joke is “The intro was great, they should make a whole song of that.”). Which, in fact, was a lot of what put me off even trying it for so long - the stereotype of a bunch of men shouting into a microphone so hoarsely as to be incomprehensible.
Maybe what I really want that often my experience of metal almost gives is ‘chamber music for rock band’. This might sound like I dislike metal as musical genre / set of genres but so far I have liked a fair chunk of what I have tried . What I am realising at the moment is that a lot of the more melodic(?) strains of metal come across to me as more… musically dense(?) than a lot of the rock music I listen to. So I am possibly responding to it more as if I were listening to art music than to pop music, and then from that perspective lyrics, especially performed harshly, will interfere with what I am trying to get out of it .
So I feel like I understand a bit better what I think of metal now.
But sometimes vocals make a pleasing line too. As I write this am trying out the album Paradise Lost by Symphony X and enjoying it a great deal. Assuming nothing happens to change my mind, I should add their name to a list and eventually go buy their albums.
 So far what suits me best is the region where it crosses over into drone music. Sun O))) does exceedingly pleasant things to me.
 Possibly for similar reasons I am not in the habit of enjoying opera, possibly not.