I think metal ballet could be interesting, though I'm not sure I'd personally enjoy it. I'd like to see an example. I tend to like ballet, it's the metal that can get on my nerves - though if it were well-chosen, it would probably be cool.
Excuse me, but I believe ballet is done on abrasive surfaces, which is on topic.
Frodo, here's link to Apocalyptica's Path. There's a lot more in YouTube, just search if you're interested.
Whoa, whoa, who said they were unnecessary?