Prety much any bookshelf speakers should be fine for Metal. I have Monitor Audio BR 1's. I just brought them as speakers in a sale with no idea how good they would be. I'm currently listening to lots of Metal, I had Machinne Head all day yesterday, Some Malevolent Creation and Massacre today with some Masterplan later. I think it's a lot to do with how well they are driven as even some bad sounding albums like some crusty Blackmetal I was listening to sounded nice and clear.
And as said already, it depends on the room size/shape. Make sure you get some think gage speaker cable as thin stuff will just squash the signal and make the bad metal albums sound worse.
I found cables have made more difference in how good things sound but I'll leave that up to you if you want to try some mid priced interconnects £35 and up to see if that helps with the sound.
If you're in England, the Bristol Sound and vision show is coming up in Feb. I would attend it as you can hear more speakers and talk to the people who make them and play some of your own music if you ask for a private listening session. You get show discount too. Same for the interconnects.
I recommend The Chord Company but only because that's how I've got my system sounding so good and they won't just suggest their most expensive. They will advise what is best for your set up.