i would also say black sabbath i dont know if any other people can realize this but toni iommi's guitar riffs and solos are all blues based solos and definitly said by The Colonel said Led Zeppelin is almost exactly what you are looking for.. but with all rock & roll (metal included) it was completely formed from Blues.. so every song out their has deep roots to blues so your not particular going to find a band that is exactly metal/blues but more or less a few bands with a few songs like that....