Though there are no direct metaphors, Tennyson uses a variety of poetic devices in his 1851 poem "The Eagle." Most notable is his use of simile (which is itself a kind of metaphor) and personification. The last line of the poem employs a simile to describe the way the eagle dives to the ocean below:
The wrinkled sea beneath him crawls;
He watches from his mountain walls,
And like a thunderbolt he falls.
The comparison to a thunderbolt is meant to illustrate the eagle's speed, strength, and inevitability; Tennyson's eagle evokes a thunderbolt's sudden, powerful, and unstoppable nature.
Tennyson also uses personification, most likely to allow the reader to better connect with the eagle, as people empathize with other people more strongly than with birds. Tennyson uses words like "hands" and "stands" to make the eagle seem more like a human being. Tennyson also never uses the word "eagle" in the whole poem—only "he"—making it easier for readers to interpret the eagle as more of a human figure.
Tennyson wrote this poem after writing poetry for some twenty-five years already. There is some speculation as to whether the end of the poem is meant to reflect simply an eagle diving down to the ocean or, rather, an eagle dying, considering that the verb "falls" is used as opposed to a more active verb like "dives" or "flies." Some who believe that the eagle dies see the poem as an homage to Tennyson's beloved college friend, Arthur Hallam, who died suddenly at the age of 24. However, Hallam's death was in 1833, and Tennyson spent seventeen years writing In Memoriam, a lengthy collection of poems commemorating his late friend. In Memoriam was published on June 1, 1850, the year before "The Eagle" was written, so it is unlikely that this poem too centers around the loss of his friend nearly twenty years earlier. In this context, the final sentence can most logically be interpreted to mean that the eagle does in fact dive toward the ocean rather than die before plummeting into the sea.