I got one word for you. Pandora. In the meantime....Thanks a bunch! some of the artists that you listed are stuff that I havn't really heard of yet :)Spoiler for:
Pandora is a website that runs what they call the Music Genome Project. You enter a song, artist or genre, and they make a free radio station based on your choice.
For example, I type in Type O Negative. They play a song typical of TON's style, and I get to give it a thumbs up or thumbs down. Depending on my choices, the program then selects another song that it thinks I ought to like... doesn't ALWAYS work out, but more often than not it does.
The only problems are that if you dont like a song, there are only so many songs you can skip in an hour, and Pandora is just a program- it's only as good as you are sure of what you like.
Pandora is only available in the U.S., Australia, and New Zealand, so you and I are out of luck. Grooveshark might have a similar function, but I'm not sure.
As for music recommendations, I will try to think of some later when I'm off work.
Of course my recommendation would be Muse, because I fucking love them, but I'd say a metal guy would be more into OoS to Black Holes. I also have a raging boner for Rise Against.
Rolling with M00s' Beethoven recommendation, which I agree with entirely, I'd also like to mention that nobody should go through life without hearing Chopin and Liszt.