Probably the most obvious is biology: a profound change in form from one stage to the next in the life history of an organism, as from the caterpillar to the pupa and from the pupa to the adult butterfly.
Or what about the magical implications of the word?
1. complete change of form, structure, or substance, as transformation by magic or witchcraft.
2. any complete change in appearance, character, circumstances; a form resulting from any such change.
And of course, when I think of metamorphosis in terms of art, M.C. Escher comes to mind with his complicated works depicting objects in the process of morphing from one kind of being into another.
Encounter by Escher