On the show mythbusters, they tried playing different genres of music to plants growing under the same conditions. The metal plants were the ones that grew the most ..
I don't really think that means metal is good for plants, but I think it might indicate it doesn't matter. :p
Music is supposed to significantly decrease aggressive behaviour of chimpanzees in a lab behaviour, but I'm not sure what the genre studied was. There's an article on it
here. My girlfriend who took a lab animal course claimed that rats responded positively to metal music, but I don't have a source to back it up!