iv always found most metal music badly recorded.
It can be really hit or miss, even within a band’s catalog. It can also get expensive because even the ones that don’t sound great can go for a LOT of money, and you can’t trust the reviews on DiscOgs AT ALL. But there are a lot of really great sounding metal records out there, and even some spectacular ones.
From my own modest collection, the following are spectacular: Avantasia’s Metal Opera 1 & 2 and Wicked Symphony (Moonglow comes close), Iced Earth’s The Glorious Burden, Rage Soundchaser, Metallica "Black" 45 RPM box from 2008, Metallica Load OG, Helloween Keeper 1 & 2, most of Magnum’s catalog, Iron Maiden Brave New World, Blind Guardian Nightfall, Nightwish Decades box, the Edguy box, the Megadeth classics (RIP, Countdown), Van Canto Voices of Fire, Opeth Morningrise, a couple from Porcupine Trees, the first 3 OG’s from Cirith Ungol, Danzig...oh and Warrant Cherry Pie sounds ridiculously good but that’s more hard rock / hair metal. There’s loads out there worth chasing, and worth playing on a great hi-fi.