At the beginning of “Ode to a Nightingale” the speaker (undoubtedly Keats himself) is wishing that he had a bottle of wine because he would like to get drunk and escape from reality. The singing of the nightingale has triggered a combination of happy and morbid thoughts. He would be happy to escape the world in which people grow old and die.
Keats was afraid of death because he thought he was going to die of tuberculosis. (He died in Italy in 1821 at the age of only twenty-six.) He didn’t want to think about it. He was developing a fondness for liquor at a very early age. You will note several references to alcohol in the poem, as well as references to hemlock and something like laudanum, which is a combination of opium and alcohol. The most subtle allusion to alcohol is contained in the lines that come later in the poem:
The coming musk-rose, full of dewy wine,
The murmurous haunt of flies on summer eves.
He imagines a big open flower full of nectar which serves in this magical world as a sort of pub where the flies gather around to drink and converse in murmurs.
But since Keats has nothing intoxicating to drink, he decides to try to escape from reality through his imagination. Bacchus was the Greek god of grape-growing and of wine (depicted in Walt Disney's Fantasia in the section devoted to Beethoven's Sixth Symphony). Bacchus would be surrounded by his “pards,” or male and female companions, because he was a very convivial type of god. Keats will use poetry instead of wine, although his dull brain is a handicap without being stimulated by the alcohol his body keeps craving. But he manages to make it to the hiding place of the singing nightingale.
The phrase “Tender is the night” was used by F. Scott Fitzgerald as the title of his best novel. It helps to set the mood of a warm, peaceful night. The Queen Moon is simply the moon, and her starry Fays are the stars—but the poet can’t see them (in his imagination) because he is hidden in the shadows under the trees and bushes, and the only light is a dim glow which seems to be blown in with the breezes.
He has taken the reader with him into a world which is seldom seen, the world of the immortal nightingale. Keats uses his vivid imagination to depict that world. He continues to escape farther and farther from reality in imagination until he reaches two of the most beautiful lines in English literature. He says that the nightingale’s voice is "the same that ofttimes hath
Charm’d magic casements, opening on the foam
Of perilous seas, in faery lands forlorn."
But the word “forlorn” brings him back to reality, and his poem quickly ends.