Well, most power metal is very D&D. Not Sonata Arctica, though, since their stuff is more like "unrequited love gone horribly, horribly wrong and now my life sucks and I must whine" instead of the typical power metal tone of "with my epic sword of victory I shall vanquish the evil hordes of the Abyss" or "me and my leather-clad Viking brothers with bulging, oiled muscles will honourably lay waste to this opposing army in an orgy of blood". Not that Sonata Arctica doesn't roxxor my boxxorz, it's just that it's not D&D. Except for "Wildfire", maybe.
There's one song, though, by the Finnish band Kilpi ("Shield"), called "Sumun maa" ("Land of Mist") that reminds me very vividly not only of D&D, but also our Living Greyhawk region, the Principality of Naerie and its themes. It's uncanny.
Wagner's Ring Cycle also has a definite D&D vibe going, but then, some metal bands have been known to state that Wagner was the first heavy metal composer...
Edit: Man, it was downright treasonous of me not to mention Teräsbetoni, the Manowar of Finland, the best heroic heavy metal band of all time. They are so D&D it hurts.
Could you please not cut off my other arm, now?