The song of ice and fire
The song of ice and fire is a subject of a prophecy, and is eponymous for A Song of Ice and Fire, the series of epic fantasy novels. The song of ice and fire is said to belong to the prince that was promised, but its content remains unknown.
In her visions at the House of the Undying, Daenerys Targaryen sees a man (Rhaegar Targaryen), and overhears him talking to a woman (Elia Martell) who is nursing a baby. "Aegon. What better name for a king... He is the prince that was promised, and his is the song of ice and fire"; When Rhaegar's eyes meet Daenerys's, he says (either to her or Elia), "There must be one more. The dragon has three heads," and he picks up a silver harp and begins to play.
However, neither Daenerys nor Ser Jorah Mormont know what "the song of ice and fire" means. It is implied that there is a connection between the song, the promise, and Daenerys herself. This is established more clearly when Maester Aemon identifies Daenerys as the "prince" that was promised.
The phrase "ice and fire" is also mentioned in the Reeds' oath of loyalty to Bran Stark. The phrase "ice and fire" appears as an example of opposites. The phrase is also used to mean direction, and is used to refer to the world by Maester Yandel in his eponymous book The World of Ice and Fire.
The phrase may also refer to a union of House Targaryen and House Stark. The Pact of Ice and Fire was an agreement made between Prince Jacaerys Velaryon and Lord Cregan Stark during the Dance of the Dragons civil war, that a royal princess should marry into House Stark in exchange for their support of the blacks, but it was never fulfilled.
It's no song I've ever heard.
They laid them north to south, from ice to fire...
Jojen and Meera Reed: To Winterfell we pledge the faith of Greywater. Hearth and heart and harvest we yield up to you, my lord. Our swords and spears and arrows are yours to command. Grant mercy to our weak, help to our helpless, and justice to all, and we shall never fail you.
Jojen Reed: I swear it by earth and water.
Meera Reed: I swear it by bronze and iron.
Jojen and Meera Reed: We swear it by ice and fire.
There is ice and there is fire. Hate and love. Bitter and sweet... Winter and summer. Evil and good. Death and life. Everywhere, opposites. Everywhere, the war.
Behind the Scenes
I mean... Fire is love, fire is passion, fire is sexual ardor and all of these things. Ice is betrayal, ice is revenge, ice is… you know, that kind of cold inhumanity and all that stuff is being played out in the books.
- A Clash of Kings, Chapter 48, Daenerys IV.
- A Clash of Kings, Chapter 63, Daenerys V.
- A Feast for Crows, Chapter 35, Samwell IV.
- A Clash of Kings, Chapter 21, Bran III.
- A Storm of Swords, Chapter 9, Bran I.
- A Storm of Swords, Chapter 24, Bran II.
- A Storm of Swords, Chapter 25, Davos III.
- A Game of Thrones, Chapter 72, Daenerys X.
- The World of Ice & Fire, The Glorious Reign.
- The World of Ice & Fire, The North: The Lords of Winterfell.
- George R.R. Martin: "Trying to please everyone is a horrible mistake" Adria's News