"The blues was like that problem child that you may have had in the family. You was a little bit ashamed to let anybody see him, but you loved him. You just didn't know how other people would take it." --B.B. King
"Metal confronts what we'd rather ignore. It celebrates what we often deny. It indulges in what we fear most. And that's why metal will always be a culture of outsiders." --Sam Dunn, Metal: A Headbanger's Journey
To me, either one of these quotes could be used interchangeably to explain the spirit of blues, jazz, or heavy metal; although I'm sure there are plenty of music enthusiasts that would disagree. But there are more than just shared stylistic traits linking the genres: There's a shared DNA that unites them at their sonic foundations.