Once upon a time there was a rock. The rock really want to be a sedimentary rock, but sadly he was an igneous rock.
Hello I'm Bob the Rock!
One day while Bob was taking a stroll it started to rain...a lot. Bob started to crack and break into sediments. He was eroding away because of the extreme weather.
After the storm, Bob wasn't a rock anymore, but sediments. After awhile, Bob's sediments started to compact together. He was slowly becoming a sedimentary rock.
In the end, Bob the rock cooled after he melted. This caused him to become an igneous rock, like what he was in the beginning. Bob the rock learned he should be happy with what he is.
Bob was so happy he was finally a sedimentary rock, but he realized he wanted to be a metamorphic rock even more. So Bob decided he was going to go through a process of heat and pressure to be what he wanted to be: a metamorphic rock.
Bob was a metamorphic rock now after being put in heat a pressure. But there was bad news, Bob was melting because of lava from a volcano