The Rock cycle is one of the natural processes that occur in the Earth. In this cycle, an igneous rock can change into sedimentary or metamorphic rock, depending on the process involved.
For example, weathering and erosion can turn an igneous rock into a sedimentary rock, where the water can break rock into pieces and may be buried layer after layer underneath the earth's surface. These rocks are also moving continuously, rubbing each other off, creating friction and heat.
In the process, the heat and pressure bakes the rocks, forcing them to recrystallize and form into a metamorphic rock.