Leda is one of Zeus's many conquests (or victims depending on how you look at it). He seduced her in the form of a swan. As a result Leda laid two eggs containing her four children: Castor and Clytemnestra to her husband, Tyndareus, and Pollux and Helen to Zeus, King of the Gods. All of Leda's children go on to have stories of their own, Helen is indeed the face that launched a thousand ships bringing about the Trojan War, Clytemnestra murdered her husband and in turn is murdered by her son Orestes, and Castor and Pollux were Argonauts and involved in many adventures. But these are all stories for another time.
"My own fatherland, Sparta, is not without fame, and my father is Tyndareus; but there is indeed a story that Zeus flew to my mother Leda, taking the form of a bird, a swan, which accomplished the deceitful union, fleeing the pursuit of an eagle, if this story is true." (Euripides, Helen, 1.17-20)
|Leda by Alfredo Sabat, 2007|
|Leda and the Swan by Cesare de Sesto, 1510-1515 after a painting by Leonardo da Vinci|
|Leda and the Swan by Alexandre Voronkov, 1997|
|Leda and the Swan by David Jermann, 1997|
|Leda by Gustav-Adolf Mossa, 1906|
|Leda by Norman Lindsay, 1995|
"Leda, meekly reclining under the wings of a swan." (Ovid, Metamorphoses, 6.109)
|Leda with the Swan by Correggio, 1531-1532|
|Leda con Cisne by Giovanni Boldini, 1860|
|Leda and the Swan by Jacopo Robusti Tintoretto|
|Leda and the Swan by Jerzy Hulewicz, 1928|
|Leda and the Swan, 16th Century|
|Leda and the Swan by Peter Paul Rubens, c. 1598-1600|
And here's a version by Rubens.
Leda and the Swan by Paul Cézanne, c. 1820-1822
Above the staggering girl, her thighs caressed
By the dark webs, her nape caught in his bill,
He holds her helpless breast upon his breast.
How can those terrified vague fingers push
The feathered glory from her loosening thighs?
And how can body, laid in that white rush
But feel the strange heart beating where it lies?
A sudden shudder in the loins engenders there
The broken wall, the burning roof and tower
And Agamemnon dead.
Being so caught up,
So mastered by the brute blood of the air,
Did she put on his knowledge with his power
Before the indifferent beak could let her drop?"
(W.B. Yeats, 'Leda and the Swan', Collected Poems, 1994)
Leda and the Swan by François Boucher, 1741
|Leda and the Swan by Giovanni Boldini, 2010|
|Leda and the Swan by Paul Prosper Tillier|
|Leda Atomica by Salvador Dali, 1949|
|Leda and the Swan by Lelio Orsi|
|Leda and the Swan by Gustave Moreau, 1865-1875|
The story of Leda's children does vary from what I wrote above, in some cases it is a single egg, and the combination of which children are born from in changes amongst sources as well.
|Leda with the Swan and Her Children by Vincent Sellaer|
|Leda and the Swan by Jacopo Pontormo, 1512-1513|
|Leda by Giampietrino, 1530|
There were just so many pictures of Leda that I had to stop or my computer may have passed out. If you want to check out more images concerning Leda, then I'd recommend Júpiter y leda which has an extensive collection laid out in chronological order.