What is the Rock Cycle? The Rock Cycle is a naturally occurring cycle, which makes rocks form into a different rock. The three types of rocks are Igneous, Metamorphic, and Sedimentary. What happens? Igneous and Sedimentary can form into Metamorphic by heat and pressure. Metamorphic and Sedimentary can form into Igneous by melting and cooling. Igneous and Metamorphic rocks can form into Sediments by weathering and erosion, and then into Sedimentary rocks by computation and cementation.