No. Metro is exclusively single-monitor (one of the worst things about it, IMO). This is most obvious if you launch an app on one monitor and then go to bring up the Start Screen on your other - it closes the app that was up on the first monitor!
The only way to do this would be with something like EyeFinity, where you trick the system into thinking your displays are one very large display - but that changes the behavior of other things in ways you might not like.
(Just be glad you only have two monitors - trying to hit the corners to bring up the charms bar is almost impossible when you have a two-by-two or larger array of monitors.)