Upon their emergence from the very loudest corner of Austin’s music scene more than a decade ago, the Sword were decried by quite a few around the country as a gimmick band, merely aping the monolithic riffage of Black Sabbath and Thin Lizzy. The conventional wisdom was that the nostalgia couldn’t last. Five albums later, the Sword has put that sort of thinking to rest. Now a stalwart of American heavy metal, the group has helped inspire a new wave of interest in throwback guitar thunder, and not least of all in their home state. Whenever they play Houston, their local fans give them a welcome befitting conquering heroes.