With regard to John Keats' poem, "Ode to a Nightingale," there are several literary techniques he employs. Keats' employs a vast number of literary devices to make his poetry more alive to its reader. I will give you a sampling.
In the first stanza, "Lethe-wards" uses an allusion (Lethe) to the mythological river one passed through after death. Drinking from the River Lethe brought forgetfulness so that the one who had died would not miss his former life. In stanza two, Keats uses personification multiple times, as in:
Full of the true, the blushful Hippocrene,
With beaded bubbles winking at the brim,
In the above, the author refers to bubbles winking, when winking is a human characteristic. In the third stanza, personification is used several times again.
Where beauty cannot keep her lustrous eyes,
Or new Love pine at them beyond to-morrow.
In this, beauty does not have eyes, and love cannot "pine" (which means to "yearn" or "ache") for something. The fourth stanza uses repetition, in "Away! Away!" In the fifth stanza, there is again personification, but also wonderful imagery, especially with "...The murmurous haunt of flies...":
And mid-May's eldest child,
The coming musk-rose, full of dewy wine,
The murmurous haunt of flies on summer eves.
Stanza six provides personification again, directed to the nightingale itself:
While thou art pouring forth thy soul abroad
In such an ecstasy...
Stanza seven uses alliteration, which is when a group of words all begin with the same sound, such as "self-same song." This stanza also alludes to the Biblical story of Ruth, living among people not her own, homesick, in the cornfields, while the eighth and last stanza uses a simile to compare the word "forlorn" and a "bell":
Forlorn! the very word is like a bell
To toll me back from thee to my sole self!