"Metamorphosis" implies "changing forms". Life requires going through stages of transformation - changing forms or stages of life. Before you are a baby you are a fetus, after birth you are the small little creature. You can't even walk, but later you start crawling, followed by walking, later on you're talking, one day you're going to school. Eventually you grow up and become fully functional. A worm turns into a butterfly. You are like a butterfly who had once been a worm. Now, what's next?