Now, about Melnitsa.

As I mentioned earlier, Melnitsa has very atmospheric music. It's unusual, and that's its strength. The lyrics (at least the ones I've listened to) are filled with beautiful expressions, vivid metaphors, and other beauties of the Russian language.
Of course, Melnitsa's music isn't for every occasion or mood, but that's not necessarily a bad thing.
If we compare it to Slipknot, you can find tons of similar music, but finding something similar to Melnitsa's music... I think it's possible, but you'll have to put in some effort.