Only an intrusive igneous rock forms underground, but you can argue that all metamorphism occurs underground. The issue here is that when the metamorphism is thermal, often the ground it is under has only just been formed (i.e. a lava flow).
To avoid confusion, only regional metamorphism can take place underground. The rocks formed by regional metamorphism and intrusive magma cooling are rocks with crystalline texture.
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They form underground from the cooling and solidification of magma.
Granite is an igneous rock that cools deep underground. It is formed from the slow cooling of molten rock below the Earth's surface, allowing large mineral grains to form.
Igneous rock typically begins as magma, which is molten rock located beneath Earth's surface. This magma can solidify underground to form intrusive igneous rock or erupt onto the surface as lava and cool to form extrusive igneous rock.
Intrusive igneous rocks
