What will be best for metal?
Or recommend other if there is a better in this price range
I have a biased opinion, but I can personally say that the Fidelio X1s are great for metal so long as you're forgiving of the edgy treble. It sounds a little more artificial than other headphones, but it's not nearly the worst offender compared to other headphones.
If you're looking for something for metal, you might like to consider Beyerdynamic DT880s. They have sparkle in the highs, so it'll bring out the cymbal banging. Otherwise, they sound pretty neutral. If you prefer bass to treble, then the Fidelio X1s will scratch your itch. Can't really speak for the Denon D600s.
If you do consider the Beyerdynamic DT880s, keep in mind you'll probably want to amp them. They aren't the hardest to drive, but I wouldn't really go and plug them into any PC (or source, for that matter) and expect them to work. If you want something that doesn't need an amp, go with the Audio-Technica AD900X. Also, the DT880 Pro and Premium are pretty much the same headphone, except the Premium is slightly more comfortable.
That all said, if it's your first shot at a pair of headphones in this price range, the Philips Fidelio X1s are fantastic, though I don't think they're quite the best for metal. I find them more enjoyable for most rock as opposed to metal.