Hmmm, comparing a band to others only works if the person you're telling knows that sort of music. Now, in most cases that's all fine and well because they might well do. But if I tried to describe say Xasthur to you...I might well start of saying "Well, they're a type of Black Metal" and you'd quickly say "What's Black Metal?"*
I guess, it's like trying to describe an object someone's never seen before, like a tree to an alien creature..if you didn't have a tree to show them, you could get all the big things across if they spoke English couldn't you? Be like saying if the music if fast or slow, what sort of tone it uses, what instruments, how they are in the mix, thick or thin sounds, how they play, do they do tech/solo stuff or not, etc, etc. And if the alien knew what some trees where like but not others...you could fill in the fine details with comparison.
Sorry for all the crappy examples, but I'm trying to keep on safe non-musical ground here.
*Yes I'm making a sweeping judgement by assuming you don't Black Metal, but it's a quick and dirty example.
