Here's how it works:

* Heat: The Earth's interior is very hot. This heat can come from magma rising from deep within the Earth, or from friction generated by the movement of tectonic plates.

* Pressure: As tectonic plates collide, they push against each other, creating immense pressure. The weight of overlying rocks also contributes to pressure.

These combined forces cause changes in the mineral composition and texture of the original rock, transforming it into a metamorphic rock. Here are some examples:

* Shale (sedimentary rock) can become slate, schist, or gneiss under different levels of heat and pressure.

* Limestone (sedimentary rock) can become marble.

So, while the movement of Earth's crust is a key factor in metamorphic rock formation, it's the heat and pressure that are the direct drivers of the transformation.