Metamorphic rocks are rocks formed by modification in the interior of the Earth through metamorphism with heat, pressure and chemical fluids. Plastic deformation is the mode of deformation in which the material does not return to its original norm after being deformed with irreversible thermodynamic changes. Both are related in that the metamorphic rocks were created by means of modification by thermal changes among others and the plastic deformation does not make a creation but a deformation, however, both refer to the change that the rocks and their behavior can have by means of treatments.