In "Sailing to Byzantium," the theme of art is conveyed through the speaker's desire to be turned into a mechanical golden bird who can sing at the royal court of ancient Byzantium.
The speaker opens the poem by explaining that he is an aging man, comparing himself to a "tattered coat upon a stick." He says that the real world he lives in is no place for an old man, teeming as it is with new life. Fortunately, he has a soul that soars higher than his numeric age, and he can imagine himself in a different world—that of Byzantium.
In the third part of the poem, the speaker asks the "sages" (wise men) to respond to the longing of his soul and release him from his body,, which will die to become, instead, an immortal work of art. He calls this transformation becoming part of the "artifice of eternity."
The speaker believes that if he can be fashioned into a work of "artifice," a mechanical bird, he will go on for ever, singing to the "lords and ladies" of Byzantium.
Becoming a mechanical bird that sings is a fitting end for the speaker, who is a poet "singing" verses to his audience.
Like other poets before him, such as John Keats, Yeats pits the real world of living, growing, and ultimately dying against the world of art, which, though static, goes on forever.