Rocks don't directly change from metamorphic or sedimentary to igneous rocks. The transition involves a melting and cooling process, which is the defining characteristic of igneous rocks. Here's how the process works:

1. Heat: Both metamorphic and sedimentary rocks can be subjected to intense heat, either from:

* Magma: Molten rock beneath the Earth's surface can heat surrounding rocks.

* Plate Tectonics: Subduction zones, where one tectonic plate dives beneath another, generate friction and heat.

* Volcanoes: Volcanic eruptions bring magma and heat to the surface.

2. Melting: When exposed to sufficient heat, metamorphic or sedimentary rocks will melt, transforming into magma.

3. Cooling and Solidification: The magma, whether it stays underground or erupts onto the surface as lava, will eventually cool and solidify. This cooling and solidification process is what creates igneous rocks.

Here's a breakdown:

* Metamorphic to Igneous: Metamorphic rocks subjected to intense heat will melt into magma, which then cools and solidifies to form igneous rocks.

* Sedimentary to Igneous: Sedimentary rocks, when exposed to enough heat, will also melt into magma and then solidify as igneous rocks.

Important Note: The process of changing a metamorphic or sedimentary rock to an igneous rock is irreversible. Once a rock has melted and solidified, it becomes an igneous rock and can only be transformed into another rock type through the rock cycle's other processes (weathering, erosion, deposition, etc.).