Yes, I also feel that it is probably more accepted for men to enjoy metal, since it matches the biological/cultural characteristics of men.
The typical gender characteristics tend to be that men are tough, unmoved, aggressive and commanding, whereas women are sweet and tender, non-confrontational and meek, so metal is probably more associated with men for that reason.
I would say that I personally have a very typical feminine personality in that regard, so people often seem surprised when they find out that I have learned to enjoy metal.