She is introduced by a light. When Gerðr raises her arms to open the door of her father's hall, the brightness off them fills the air and the sea, and every world is made bright by her — which is why Freyr, watching from a seat he should not be sitting in, becomes ill.
That image is the whole of Gerðr's description in the sources, and it is one of the finest in Eddic poetry. Everything after it is a negotiation she does not want to have.
What Skírnismál actually does
Freyr's servant Skírnir rides to Gymir's court and finds Gerðr. She receives him properly — asks who he is, offers him mead — and then refuses, in order, everything he brings.
He offers eleven golden apples. No. He offers the ring Draupnir, which multiplies itself every ninth night. She says her father has gold enough and she will not share her wealth with Freyr.
Then Skírnir stops offering. He threatens to cut off her head with the sword in his hand, and to kill her father with it. She answers that she will not be forced by threats, and that if Gymir finds him there they will fight.
So he moves to the third stage, and it occupies most of the poem: a curse, carved with a gambanteinn, a wand or magic twig. She will sit on the eagle's mound facing away from the living world toward Hel. Food will be more hateful to her than the serpent is to men. She will be a spectacle to be stared at. She will be tormented by a three-headed giant or live unmarried and desiccated. She will be driven mad with longing that has no object — and here he names the runes he is cutting: þurs first, and then three more, standing for lust, burning and unbearable restlessness. He adds that he can cut them away again if he chooses.
Gerðr's next words are the acceptance. She offers him the frost-cup full of old mead, says she never thought she would love one of the Vanir, and names the place and the time: the grove called Barri, in nine nights.
How to read it, and how not to
The dominant scholarly reading is a hieros gamos: the shining god of fruitfulness courting the frozen earth, with nine nights as the interval between sowing and germination, and the curse as the threat of a failed season. Gerðr's name is connected to garðr, an enclosure or a fenced field, and that supports the reading well — she is literally the enclosed ground.
The reading is probably right about what the myth is. It does not change what the poem says. The text spends more than twenty stanzas on the threats, in escalating and specific detail, and gives Gerðr consent only after they are complete. A poet who wanted a seasonal allegory could have written a much shorter and less unpleasant one, and this one did not.
It is also worth noticing what Freyr is not doing. He never goes himself. He sends a servant with his sword — the sword he will not have at Ragnarök — and stays home. The most quoted stanza in the poem is his complaint about waiting: one night is long, two are longer, and a month has often seemed shorter to him than half a wedding-night's waiting. That line is regularly reproduced as a piece of tender love poetry, entirely detached from the twenty stanzas of coercion that made the appointment.
The rest of what is known
Gerðr's father is Gymir and her mother is Aurboða, both giants, and Snorri repeats this in Skáldskaparmál, adding that she is the fairest of all women. He also lists her among the goddesses in Gylfaginning, which is the standard fate of a giantess who marries into Ásgarðr — see Skaði.
Ynglinga saga makes her and Freyr the parents of Fjölnir, the first of the Ynglingar, ancestor of the Swedish kings — who dies by falling into a vat of mead in a Danish hall. The Norwegian royal line and eventually the historical kings of Norway claimed descent through that lineage, which means Gerðr the giantess is a great-grandmother of medieval European monarchy in Snorri's reckoning.
She appears in kennings and in the Skáldskaparmál name-lists and nowhere else. There is no cult evidence.
Skirnismal in the seminar room
Skírnismál has attracted disproportionate modern attention — it is the Eddic poem most often set for undergraduate discussion, precisely because the gap between the standard interpretation and the plain sense of the text is so wide. It has also been staged and adapted, and Gerðr has appeared occasionally in fiction, usually softened.
The honest way to present her is as the sources have her: a giant's daughter with an entirely reasonable objection, worn down by curse-magic, who then does not weep, does not resist further, and names the terms of the meeting herself. See the Norse family tree for how comprehensively the gods married into the group they fought, and the Norse overview for the tradition.
Is the curse magic or persuasion?
The poem treats it as operative magic, not rhetoric. Skírnir carves runes on a wand while speaking, names the specific runes, and states that he can reverse the carving — which makes the threat a physical act with a physical remedy, in exactly the way Norse rune-magic is described elsewhere, including in Egils saga, where a wrongly-carved rune makes a girl ill and correctly-carved ones cure her. Gerðr is not being talked round. She is being subjected to something, and she yields when the carving is complete.
Why nine nights at Barri?
Nine is the pervasive Norse ritual number — nine nights on the tree, nine worlds, nine mothers, nine-yearly sacrifices at Uppsala and Lejre. Beyond that, Barri is usually taken to mean a leafy or barley-field grove, from barr, which makes the appointed place a field of grain, and the nine-night delay reads naturally as an interval before growth. That is the strongest single piece of evidence for the fertility interpretation, and it is a place-name rather than anything the characters say.