While filming a segment for his “Conan O’Brien Must Go” series, Conan O’Brien joined “slush metal” band Cringe Blizzard onstage in Feldkirch, Austria. You can see footage of him attempting metal vocals below. This news comes after Cringe Blizzard vocalist Katherina previously appeared on O’Brien’s “Conan O’Brien Needs A Friend” podcast and offered to teach…