Beyond this, the uses of shapeshifting, transformation, and metamorphosis in fiction are as protean as the forms the characters take on. Some are rare — Italo Calvino's "The Canary Prince" is a Rapunzel variant in which shapeshifting is used to gain access to the tower — but others are common motifs.

Punitive changes

In many cases, imposed forms are punitive in nature:

Athena transformed Arachne into a spider for challenging her as a weaver.

Artemis transformed Actaeon into a stag for spying on her in her bath.

In some variants of the fairy tales, both The Frog Prince and Beast, of Beauty and the Beast, were transformed as a form of punishment for some transgression.

Circe transformed all intruders into her home. In Nathaniel Hawthorne's Tanglewood Tales, "she changes every human being into the brute, beast, or fowl whom he happens most to resemble."

In George MacDonald's The Princess and Curdie, Curdie is informed that many human beings are turning into beasts, and is assisted by beasts that had been transformed and are working their way back to humanity.

In The Chronicles of Narnia, Eustace is transformed into a dragon, and Rabadash into a donkey, as punishments.

In mythology, the punishment is often a metamorphosis, and in fact may be myths of origin.
In most works of fiction, the changes are usually a temporary transformation. If the punishment was just, the character can often re-gain his form on learning the lesson it instructed him in; if unjust, the restoration is merely dependent on discovering the trick of it.
 

Transformation chase

In many fairy tales and ballads, as in Child Ballad #44, "The Twa Magicians", a magical chase occurs where the pursued endlessly takes on forms in an effort to shake off the pursuer, and the pursuer answers with other shape-shifting, as, a dove is answered with a hawk, and a hare with a greyhound. The pursued may finally succeed in escape or the pursuer in capturing.

In other variants, the pursued may transform various objects into obstacles, as in the fairy tale "The Master Maid", where the Master Maid transforms a wooden comb into a forest, a lump of salt into a mountain, and a flask of water into a sea. In these tales, the pursued normally escapes after the three obstacles.

In a similar effect, a captive may shape-shifting into order to break a hold on him. Proteus's shape-shifting was to prevent heroes from forcing information from him. Tam Lin, once seized by Janet, was transformed in her arms by the faeries to keep Janet from taking him, but as he had advised her, she did not let go, and so freed him.

Patricia A. McKillip made use of this motif at one point in the The Riddle-Master of Hed trilogy: a shapeshifting Earthmaster finally wins its freedom by startling the man holding it.
 

Powers

One motif is a shape change in order to obtain abilities in the new form. Berserkers were held to change into wolves and bears, which could find. In many cultures, evil magicians could transform into animal shapes and thus skulk about.

This use, though rare in older fiction, is perhaps the most common in modern fiction. Several superheroes — Beast Boy, The Martian Manhunter, Chameleon Boy/Chameleon, Morph, Mystique — have it as their sole power. The Harry Potter series contains both Animagi who can change to a single form and Metamorphmagi who can alter their appearance.
Even creatures from folklore may regard their other forms as abilities. The werewolf in Poul Anderson's Operation Chaos uses his wolf form to track and to fight, and never suffers from the desire to attack humans so common in legend.

Bildungsroman

A young character may learn of his shape-shifting abilities, and exploring them becomes part of a Bildungsroman. Mavin Manyshaped and her son Peter in Sheri S. Tepper's True Game novels are both shifters, being a subspecies of humans having this power, and in both, the learning of their abilities is a large portion of their growing up.

For a very different effect, T. H. White had Merlin transform Arthur into various animals in The Sword in the Stone, as an educational experience. Although the lessons are very different, the Bildungsroman element is in common.

Needed items

Some shape-shifters are able to change form only if they have some item, usually an article of clothing. Most of these are innocuous creatures — even if they are werewolves. In Bisclaveret by Marie de France, a werewolf can not regain human form without his clothing, but in wolf form does no harm to anyone.

Another such creature is the selkie, which needs its sealskin to regain its form. In "The Great Selkie o' Suleskerry" the (male) selkie seduces a human woman but does no further harm.

The commonest use of this motif, however, is in tales where a man steals the article and forces the shape-shifter, trapped in human form, to become his bride. This lasts until she discovers where he has hidden the article, and she can flee. Selkies feature in these tales. Others include swan maidens and the Japanese Tennin.
Various forms of fairytale fantasy have taken up these creatures and incorporated them into modern day works. Jane Yolen took up the notion of selkie in Greyling and transformed it into a foundling tale.

Usurpation

Some transformations are performed to remove the victim from his place, so that the transformer can usurp it.

Bisclaveret's wife steals his clothing and traps him in wolf form because she has a lover.
In Brother and Sister, when two children flee their cruel stepmother, she enchants the streams along the way to transform them. While the brother refrains from the first two, which threaten to turn them into tigers and wolves, he is too thirsty at the third, which turns him into a deer.

The Six Swans are also transformed by their stepmother, as are the Children of Lir in Irish mythology, into swans. In The Laidly Worm of Spindleston Heugh, Princess Margaret is transformed into a dragon by her stepmother; her motive sprung, like Snow White's stepmother's, from the comparison of their beauty.

A witch, in The Wonderful Birch, changed a mother into a sheep to take her place, and had the mother slaughtered; when her stepdaughter, with her dead mother's aid, married the king, the witch transformed her into a reindeer so as to put her daughter in the queen's place.

Modern fiction also includes this motif: Mary Stewart's A Walk in Wolf Wood revolves about revealing that one man is an imposter, taking the form of a man who is living as a wolf in the woods, and Patricia A. McKillip has her shapeshifters, in the Riddle-master trilogy, use their forms to take the place of others.

Unadvised wishes

Many fairy-tale characters have expressed inadvised wishes to have any child at all, even one that has another form, and had such children born to them. At the end of the fairy tale, normally after marriage, such children metamorphize into human form.

"Hans My Hedgehog" was born when his father wished for a child, even a hedgehog. Even stranger forms are possible: Giambattista Basile included in his Pentamerone the tale of a girl born as a sprig of myrtle, and Italo Calvino, in his Italian Folktales, a girl born as an apple.

Sometimes, the parent who wishes for a child is told how to gain one, but does not obey the directions perfectly, resulting in the transformed birth. In Prince Lindworm, the woman eats two onions, but does not peel one, resulting in her first child being a lindworm. In Tatterhood, a woman magically produces two flowers, but disobeys the directions to eat only the beautiful one, resulting her having a beautiful and sweet daughter, but only after a disgusting and hideous one.

Less commonly, ill-advised wishes can transform a person after birth. The Seven Ravens are transformed when their father thinks his sons are playing instead of fetching water to christen their newborn and sickly sister, and curses them.

Monstrous bridegroom/bride

Such wished-for children may be become monstrous brides or bridegrooms. Other such characters have no explanation for their forms, because their tales focus on the person who must marry them.

These tales form, broadly, three subclasses.

The hero or heroine must marry, as promised, and the monstrous form is removed by the wedding. Sir Gawain thus transformed the Loathly lady; although he was told that this was half-way, she could at his choice be beautiful by day and hideous by night, or vice versa, he told her that he would chose what she preferred, which broke the spell entirely. In Tatterhood, Tatterhood is transformed by her asking her bridegroom why he didn't ask her why she rode a goat, why she carried a spoon, and why she was so ugly, and when he asked her, denying it and therefore transforming into her goat into a horse, her spoon into a fan, and herself into a beauty.

Sometimes the bridegroom removes his animal skin for the wedding night, whereupon it can be burned. Hans My Hedgehog falls under this grouping. At an extreme, in Prince Lindworm, the bride who avoids being eaten by the lindworm bridegroom arrives at her wedding wearing every gown she owns, and she tells the bridegroom she will remove one of hers if he removes one of his; only when her last gown comes off has he removed his last skin and become a man.

The lindworm's bride was the last of a number of brides. Some other tales using this theme also have one or two who fail the task of the marriage.

In another grouping, the heroine must fall in love with the the transformed groom. Beauty and the Beast falls under this.
In the third grouping, The heroine must spend a period of time not seeing the transformed groom in human shape, except that in these tales, she invariably defies the prohibition and must therefore find her bridegroom and save him from evil magic forcing him to marry another. Two such tales are East of the Sun and West of the Moon and The Black Bull of Norroway.

Unusually, we learn in East of the Sun and West of the Moon that the prince was transformed by his wicked stepmother.

This motif is found in modern fiction mostly in the form of fairy tale fantasy. Robin McKinley retold Beauty and the Beast twice, in Beauty and Rose Daughter.