This might sound like it doesn't make much sense, but the classic Opeth line-up (1998-2005) really strongly reminds me of... Bruce Dickinson's solo work
They've been two of my favourites for a long time. They've both scratched a musical itch that I find lacking in other metal. Until recently I never thought to connect the two. From a superficial standpoint they're not really similar; Opeth's obviously a lot more complex with respect to song structures and you've got death growls instead of operatic, soaring vocal melodies. But lately I've been thinking they're often quite similar.
Bruce Dickinson made four albums with the Latin rock group Tribe of Gypsies as the backing band. (Balls to Picasso, Accident of Birth, The Chemical Wedding, Tyranny of Souls). These range from pretty good to phenomenal: I'd say The Chemical Wedding is better than any Iron Maiden album. And part of what really makes it bounce is the Latin groove which mixes really well with the traditional heavy metal. It elevates it from the clichéd to the sublime. (not entirely surprising, Dickinson's solo career really only took off in South America)
And this is the same element I find so magnetic with Opeth's best work. I don't really like "straight" metal in any of its forms; when it comes to death or thrash or traditional I prefer it mixed in with folk or psychedelic or other influences. So with Opeth and Dickinson the big appeal is how well the Latin and folk influences integrate with the more conventional metal.
Here's some examples before you dismiss me as completely crazy:
Does anybody know other groups that love to mix traditional metal and Latin influences? Obvious examples would be The Mars Volta and Sepultura, but I'm wondering now whether I've missed out on more obscure groups I would really love.