Ok I might have a little bit of trouble explaining this. I would've put it in one of the general threads but I'm not going for any specific genres (though extreme metal subs are probably preferable).

Anyway, it's a specific kinda sound I wanna hear more of from metal guitar. Especially in black/death metal it seems like a sense of "coldness" often rules the tones and timbres, and that's all well and good but some select bands have this warm-ish, cozy thing going on, with riffing that sounds like like the chords/notes melt into a gooey whole as opposed to freezing together in an icy embrace. Does that even make sense?

The best example of this I can think of would be Drudkh, who have perhaps my favorite guitar work in atmospheric black metal. Another could be Horrendous from Ecdysis and onward. Forgive me if I'm being too vague.

It's a bit a shot in the dark, but your description immediately reminded me of Totenmond's Reich in Rost. the guitar sound in that album immediately makes me think of lava

It's always hard trying to explain a certain type of sound or tone that you know what it sounds like in your head. I like your description of "Melty" tone though, i've never heard that one before XD

Perhaps try some Greek black metal.