When a metamorphic rock undergoes a change that causes it to melt, it is no longer a metamorphic rock. Instead, it becomes igneous rock.

Here's why:

* Metamorphic rocks are formed from existing rocks (igneous, sedimentary, or even other metamorphic rocks) that have been subjected to intense heat and pressure without actually melting.

* Igneous rocks form from the cooling and solidification of molten rock (magma or lava).

So, if a metamorphic rock melts, it's essentially starting the rock cycle over again, transitioning from a metamorphic state to an igneous state.