(Thinking about this more).
In a genre like heavy metal, it seems like a lot of the "lighter" stuff sounds like generic pop music with the guitars really cranked up and sounding really distorted + layered in the studio, along with the overall low end bass cranked up very unnaturally. For example, stuff like Def Leppard, Whitesnake, and especially "power ballads" type songs.
Whitesnake - Bad Boys
Def Leppard - Billys Got A Gun
For some "heavier" stuff, this style of production just makes everything sound like a "muddy" slickness. For example, a lot of metallica records sound like that. An annoying "heaviness" which seems excessive at times.
Fundamentally, that's just what makes Metal a lot of the time. Either a really fast tempo, like the Whitesnake, or a really heavy, slow beat with power chords and lots of distortion, like the Def Leppard.