O, for a draught of vintage! that hath been
Cool'd a long age in the deep-delved earth,
Tasting of Flora and the country green,
Dance, and Provençal song, and sunburnt mirth!
O for a beaker full of the warm South,
Full of the true, the blushful Hippocrene,
With beaded bubbles winking at the brim,
And purple-stained mouth;
That I might drink, and leave the world unseen,
And with thee fade away into the forest dim:

Fade far away, dissolve, and quite forget
What thou among the leaves hast never known,
The weariness, the fever, and the fret
Here, where men sit and hear each other groan;
Where palsy shakes a few, sad, last gray hairs,
Where youth grows pale, and spectre-thin, and dies;
Where but to think is to be full of sorrow
And leaden-eyed despairs,
Where Beauty cannot keep her lustrous eyes,
Or new Love pine at them beyond to-morrow.

This excerpt is taken from the middle of Keats' ode, when he's imagining turning into a bird and following the nightingale into the trees.

The speaker of Keats' poem wants to turn into a nightingale….seriously. He wants some magical potion that will make him live in nature, where the nightingale lives. Why? Because he's sick of human society. "Among the leaves," where those nightingales hang out, there's no weariness or fret or fever. There's no misery. Life is easy and beautiful.

Here we see the Romantic valorization of nature. According to these guys, nature is so much better than human society.

Here we have another ode—this one to a bird. That's pretty unusual because traditionally (like back in the days of the ancient Greeks, who were the first one to start writing these types of poems), odes were written to praise famous or important men. And here's Keats writing an ode to a bird…pretty radical. He's saying a bird is as important and as beautiful and as worthy of praise as some famous war general or king.