Symphonic metal is huge, especially in Europe and South America.
Besides the miriad of bands like Xandria, Within Temptation, Epica, Nightwish, there are bands that have 15+ members like Haggard (actually my favourite symphonic metal band), bands that have defined the genre, like Therion and bands that do the extreme symphonic, like Septicflesh, Dimmu Borgir. This metal genre has something for everyone, metalhead or not.
So, enjoy