The Rock Cycle is the process in which rocks are formed, changed, and broken down. An igneous rock can either change into a sedimentary or into a metamorphic rock; just the same that a sedimentary rock can change into an igneous rock or metamorphic rock. Factors like heat, water, and air can break and form new types of rocks in a continuous cycle.
The rock cycle never stops; it is a continuous process that occurs through time. A mountain that is composed of metamorphic rocks can easily be washed away by streams and new sedimentary rocks can be formed through this process.