Metamorphic rocks are rocks that have "morphed" into another kind of rock. These rocks were once igneous or sedimentary rocks. How do sedimentary and igneous rocks change?

The rocks are under tons and tons of pressure, which fosters heat build up, and this causes them to change. If you exam metamorphic rock samples closely, you'll discover how flattened some of the grains in the rock are.

Metamorphic rocks & fossil

Fossils can also be found in metamorphic rocks, like marble. Metamorphic rocks form from previously existing rocks, such as sedimentary rocks or igneous rocks, which are pulled deep into Earth's crust.

Deep in the Earth's crust, 30,000 feet down, there is tremendous pressure heating the rocks and pulling them like taffy. The original rock is changed by this heating and pulling and forms a metamorphic rock. Any fossils which were in the sedimentary rock will now be in the metamorphic rock,but may be stretched and deformed because of the heating and pulling.