It is rare indeed when the Finnish operatic metal band Nightwish comes to the United States. Fans of symphonic metal (like most of us in this house), upon hearing that they would be within driving distance for the first time in many years sprinted, not ran to pick up tickets for this show the moment they went on sale. I can't really describe them to you so all I can really say is take two parts power metal, one part opera, and one part old-school swords and sorcery fantasy, throw into a blender, add a shot of sulfuric acid, and …