I have both the Denon D2000 and Grado 325is, and for metal I will definitely have to recommend the Grado. They sound amazing with guitars and acoustic. The bass isn't overwhelming but punchy. Unfortunately the highs are a bit harsh, but either they don't sound as bright with burn-in, through a tube amp, or just getting accustomed to them. But I must say they are a bit heavy due to the metal alloy for the casing, and at least for me they hurt after having them on for around 2 hours.
The Denons are many times more comfortable, with more bass (I don't find them muddy, but it depends on the recording), recessed mids, and sparkly highs (in a good way). I don't find them as nice for metal and they have a bit of a more relaxed sound compared to the Grado.