Unbeknownst to me, David Ellefson of Megadeth has had an educational series on YouTube called David Ellefson's Rock Shop (Link to Playlist of all lessons). Pocketlabsworks has been working with David to create an app to build on this, providing a simple way for budding guitarists to jam along with some of the best Metal ever; in the form of Megadeth's "Peace Sells" album. Beyond that you can import your own songs and play around with different tunings and amps and do other things I barely understand. I'm most impressed by the fact that this $10 app has no In-App Purchases! You get a bunch for $10 without them trying to up-sell you on pedals or someshit.

I'll let David give you the run-down, since I don't play guitar: