One of the first steps towards identifying metamorphic rocks is to determine if it has foliation or not. Luckily, this is usually easy to do. Foliation means banding or alignment of the minerals resulting from pressure. A good example of that is the banding present in a metamorphic rock called gneiss, pronounced "nice".
This piece of gneiss formed from granite similar to the rock sample seen on the left hand side of the photo.