Here's why:

* Sedimentary rocks are formed when sediments are compacted and cemented together.

* Metamorphic rocks are formed when existing rocks (igneous, sedimentary, or even other metamorphic rocks) are changed by heat and pressure deep within the Earth's crust.

Think of it like this:

* Sedimentary rocks are like building a sandcastle - you start with loose sand and make it solid by pressing it together.

* Metamorphic rocks are like baking a cake - you take existing ingredients (the original rock) and transform them into something new through heat and pressure.