Here's why:

* Metamorphism is the process of transforming existing rocks (igneous, sedimentary, or even other metamorphic rocks) through intense heat and pressure. This process changes the rock's mineral composition, texture, and sometimes even its chemical composition.

* Heat can come from sources like magma intrusions, tectonic plate collisions, or deep burial within the Earth's crust.

* Pressure is applied through the weight of overlying rock layers, tectonic forces, or even the weight of water in the Earth's crust.

Examples of metamorphic rocks:

* Marble: Formed from limestone under heat and pressure.

* Slate: Formed from shale under heat and pressure.

* Gneiss: Formed from granite under intense heat and pressure.

Let me know if you have any other questions!