An igneous rock can change under pressure to metamorphic. A igneous rock can turn into another igneous rock by melting and solidifying, it can turn into a sedimentary rock by getting weathered then recemented, or it can turn into a metamorphic rock by being subjected to great heat and pressure
If there is too much heat or pressure, the rock will melt and become magma. This will result in the formation of an igneous rock, not a metamorphic rock. Consider how granite changes form. Granite is an igneous rock that forms when magma cools relatively slowly underground
