I totally agree with what Sydo has said, and have thought about it a bit actually. Alot of people have been ragging on Metallica for touring with the likes of Linkin Park, Limp Bizkit, Mudvayne, Deftones, ect, but if these bands bring in the younger nu-metal kids who haven't got into the older stuff, for Metallica it might help them win over some new fans. Also, if this new material is as aggressive as people have been saying, Metallica will wipe the floor with all the other bands on the bill, and show the kids what METAL is all about.
Could be interesting indeed.