Dude metal subgenres are the most different sounding subgenres you can find. Try listening to pornogrind and listen to nothing else matters by metallica. But when talking about rap we all know a general idea about what it will sound like, that's not the case with metal. I can find you metal songs that sound like planet atmosphere ambient sounds with literally 1-2 instruments, or songs that have like 15 notes per second and 300 bpm. Or you can find classical pieces adapted to metal, pop covers of metal, nu metal (basically rap-metal) and so much more. And i didn't notice they were the same subgenres, i though you picked different kind of subgenres (since that's what i mostly do when linking metal) but after 3rd song i heard the similarity and thought probably they were same or close subgenres. But trust me, you can find songs that doesn't sound anything like metal but is metal.