In the cosmic world of the Old Norse system of belief, animals were an integral part because they possessed knowledge of nature and conveyed it to humans and gods. Humans transgressing their bodily boundaries by becoming animals were therefore nothing unnatural, just slightly unusual. Fluidity, hybridity and metamorphosis were considered as simple facts of nature. In this process, body parts were integrated in animal wholes to indicate ambiguity and shape shifting, illustrating the Old Norse saying eigi einhamr, that is a person ‘not of one shape’.
However, metamorphosis and hybridity are different in ‘nature’. Metamorphosis is a process, while hybridity is not (Bynum 2001: 28 ff.). A hybrid is an entity of two or more parts and it is visible; we actually see what a hybrid is. Like the creatures in the animal styles, a hybrid is a double/triple, etc., being. Here, eagle, wild boar, snake, beast, etc. and humans constitute hybrid forms that encapsulate the power and ability of all species. The same might be seen in the hyphenated personal names with two or three names in combination: animals as well as battle/war/fight-synonyms. On the contrary, metamorphosis goes from one entity to another and is essentially narrative. The metamorphosis is a process going on from beginning to end, and is comparable to the little death of the shaman/bear/sei∂-man/women in the stage of soul journey/winter hibernation. It is a constant series of changes and replacements. Metamorphosis breaks down categories by breaching them: man becoming wolf or bear, male becoming female, youth becoming a tree, etc. In opposition to this, hybridity is about contradictions. In a hybrid form, contradictory categories are forced to co-exist, such as when man, wolf, snake, eagle and wild boar co-exist in the animal iconography. I
— (page 98) Iron Age Myth and Materiality: An Archaeology of Scandinavia AD 400-1000 by Lotte Hedeager