While the wedding day does belong to the bride and groom, some consideration of the guests should be had. I would agree to give the OK to play some "death metal" music, but it has to be interspersed throughout. Groom needs to understand that, for some of the older relatives there, it's not going to be pleasant and no one should have to endure a long string of loud, kidney vibrating music. If the DJ sees people avoiding the dance floor and people leaving the room, he needs to change quick. On the other hand, if *most* of the guests are the bride and groom's friends and of their group, the death metal may be extremely popular. You never can tell. I think you should compromise on this. Alternatively, the groom needs to compromise also.