[State Of Trance]

My brother is in the market. Here's what we're dealing with!
 

1. The man digs his metal. Seriously, you should see the beard and mane on this bro.
2. Sound leakage doesn't matter too much. My impression is that the kind of bass that metal requires would probably mean closed backs, but open backs are fine as well if they fit the other criteria.
3. Preferably $200 or less. These will be his first "real" cans and he's a college student so no Lamborghini tier cans.
4. Must not require an amp. He'll be using these on an MSI laptop and an iPod, sometimes moving from place to place.
5. Good for fairly long sessions. Comfort matters. He'll start a session while doing homework and that can last a while.
6. Must fit his ears. I don't know his exact measurements, but let's assume, for example, that my large Sennheiser 598 would be a good size for him.

 
If you have a suggestion that doesn't fulfill all parameters but is really sweet, feel free to share anyway.
 
Here's some metal as well as other random stuff that he likes. Again, though, metal is the priority.
 

1. RAUBTIER - SKJUT GRÄV TIG (Lyric Video) - YouTube
2. SABATON - To Hell And Back (OFFICIAL MUSIC VIDEO) - YouTube
3. Iron Maiden - Dream of Mirrors - YouTube
4. TYR- Sinklars visa - YouTube
5. land tyr - YouTube
6. Halsey - Gasoline (Audio) - YouTube
7. Twenty One Pilots - Stressed Out by NateWantsToBattle ft ShueTube [1 HOUR] - YouTube
8. Death Note - The World (English Cover Song) [1st Opening] - NateWantstoBattle - YouTube
9. Puella Magi Madoka Magica OST - Magic (Magia) - YouTube
10. Puella Magi Madoka Magica ED - Magia - Full Size GUITAR COVER - 魔法少女まどか☆マギカ - YouTube
11. K-ON! Ending 1 - Don't Say 'Lazy (60FPS) - YouTube
12. Blind Guardian - When Sorrow Sang - YouTube

 
He's been using nothing but earbuds his whole life, people! Let's set him off on his headphone journey!

 

[Stone Magnet]

I'd say the majority of my listening revolves around metal, so maybe I can help in guiding you a little bit. The first thing is that, while the bass is something prominent and important in the genre, I personally prefer headphones without an exaggerated bass response. There's often a lot going on in that space and I find that if it's boosted like one might want to hear in electronic music, it drowns out a lot of the mid-range articulation of the guitars and displaces other aspects while sounding boomy or muddy. The focus is not supposed to be on the bass as much in this kind of music.
 There are some genres that benefit in listening from heaphones with more coloration to them, but in my experience in listening and recording metal for some years, there's a delicate balance the engineers involved strive to achieve and searching for more a more neutral and even response across the spectrum is probably the way to go to get the most enjoyment out of your listening.
 As far as specific models or anything, that would be more difficult for me to say because my experience isn't the most broad as many other members here, but I did think it might be useful for you if I mentioned the above to help in your investigation.

 

[Monsterzero]

The term "metal" is used to describe a multitude of music styles....its almost useless at this point to try and suggest anything based upon that word.

Classic metal you will want something with  nice prominent mids and bass isnt really that needed.

If you like doom/stoner then bass is a must.

I was listening to some Priest last night with my sextetts and it sounded awesome,then I switched to Anciients,and it sounded horrid.....

I could go on but I wont.....

TL,DR

certain headphones will sound great with some metal,and not great for others.