Well, metal simply has its own culture.
That's the big point for me. It's not counter-culture, or made in a negative image of a parental culture. It's its own culture which is compatible with the past, not the present, and definitely not the dominant meme (equality).
Metal is only a counter-culture in the sense that it opposes modern society because it has its roots firmly in romantic visions from the past. After consideration one can safely conclude that in reality modern society is more counter-culture than metal is. It's a case of the loony calling the sane man crazy.
Metal deals with timeless themes such as mysticism, eternal power struggles and complex romantic themes whereas punk deals with post-50s urban jungle topics such as alienation, politics and simple romantic themes. Very few people will deny that punk is a counter-culture. Informed people won't claim that metal is a counter-culture. I also believe the metal aesthetic is based on values that lie in the past, in spirit it predates all music based on rock&roll. Once you see this it becomes easier to separate the timeless from the momentary.
Metal typically has longer songs (or songs that seem like fragments that make up a longer song) whereas punk has short songs. I think this is one of the underlying reasons that punk bands that dress themselves up as metal bands typically have boring songs. If all you want to say is "don't vote for..." or "I'm in love with..." then what's the point in 7-20 minute songs? Bands like Profanatica and Beherit get it right by not making long songs when they gravitate towards punk/grind more than Graveland or Summoning do. Meanwhile the indie black metal bands all fail with their 10+ minute political love ballads. In just a few years time there won't be anything left of the indie black metal culture (except the usual "classics" catching dust in the bargain bin) because indie black metal lacked a culture to begin with. At most the indie infiltrators will poison some weaker minds and take down some lesser individuals with them, it's only part of natural selection.