First of all there are major Bands in Rocksmith. I.E. White Stripes, Radiohead, Pantera, System of A Down, the list goes on and on. In fact there's practically no non-big time bands in Rocksmith or Rocksmith DLC, disregarding the Developers' music. Second: I'm pretty sure if Metallica, a very popular and impacting band on the music industry (regardless of my opinion on them), isn't on RS by now it's because Ubisoft or Metallica can't or doesn't want to make such deal.