I know five...

I know 5 metal operas.

Hmm...
1. Avantasia - The Metal Opera
2. Avantasia - The Metal Opera 2
3. Epidemia - Elfiyskaya Rukopis (Elven Manuscript)
4. Epidemia - Elfiyskaya Rukopis - Skazanie na Vse Vremena (Elven Manuscript - A Tale for All Times)
5. Blind Guardian - Nightfall in Middle-Earth (maybe not an opera, but it's in the same vein ;))

I know five guitar manufacturers.