I will talk more about metal music in general. Metal music shall not be seen as the big demon to fight against. Metal music will never have a negative influence on a child. This music is full of violence, so we may think that it is something bad. It isn't. It gives power to the persons that understand it, it gives a sense of belonging and it gives the strength to carry on, to go over problems. Kids should avoid norvegian black metal musicians but apart of this, such a music can only be helpful. And master of puppets is pretty good.
What other families should know
Too much violence
Too much swearing