Try take a listen to their "Bloody Kisses" album, without doubt their easiest accessible album, even with a couple of big hits on it.
Also metal is much a broader genre than speed, power and trash metal.
Such as stoner, doom, sludge or even drone metal.
Plenty of energy in these genres, just not speed wise, instead they put the truly heavy in the metal.
It's a heft thing, rather than a speed thing.
And Type O Negative in general is to the darker and heavier side of the spectrum.
Also this is rock, not Celine Dion or Pavarotti.