The very term Metamorphic, is an adjective, its synonym "changed" is the more common word. It is an apt description because metamorphic rocks are sedimentary or igneous rocks that have been subjected to significant heat and/or pressure changing their structure, but not melting to form igneous rock. For examples; limestone being compressed heated and warped to become marble, or bituminous coal being pressed into anthracite coal.
Some other adjectives that could be derived from the process of making metamorphic rocks, would be: compressed, baked, warped, hardened, softened, toasted, roasted, heated, and changed.
For your assignment you could take any two of the adjectives I listed.