Here's why:

* Formation: Metamorphic rocks form when existing rocks (igneous, sedimentary, or even other metamorphic rocks) are subjected to intense heat and pressure deep within the Earth's crust. These conditions cause changes in the rock's mineral composition and texture.

* Exposure: Over time, tectonic processes like uplift and erosion can bring metamorphic rocks to the surface, where they are exposed.

So, while the formation happens in the crust, metamorphic rocks are often found in both locations!