Opeth are death metal with a lot of mellow acoustic parts and as time went by they incoporated influences from prog in general. Melodic death metal (mostly Swedish bands as opposed to US death metal bands) mixes in clean vocals with the death growl and also offer far more variation on sound, listen to In Flames and Dark Tranquillity just to name two. In fact "Whoracle" by In Flames is probably the finest album of the melodic death metal scene. There are also prog bands like Amorphis which are influenced by death metal but are exclusively clean vocals with a lot of normal rock and other influences.

An album I recommend, which predates the mellow approach by Opeth by a number of years is Tiamat`s "Wildhoney" certainly more prog than death metal and the group draw influences from death and black metal in general.

@Unknown Soldier - thank you!
I need diversity and it seems I could find it in your recommendations, I will try it ;)

Burzum, Emperor, Enslaved, Wolves In The Throne Room, Woods Of Desolation, Xasthur, Mayhem, Wedard, Nychts, Crucifix d.ildo

That Tiamat album is great, definitely worth checking out if you haven't before.

I like more melodic metal, like Children of Bodom, I love Opeth, especially Ghost Reveries. Bands like Mayhem don't appeal to me at all, though I do like me some southern death metal, like Deicide, Obituary, and though theyr'e not from the same region, Cannibal Corpse's Gallery of Suicide is a fine album indeed.

Children of Bodom also have a very heavy power metal influence as well.

itt people who do not listen to black metal make off-topic posts about random metal bands they like.