The literary element of William Blake's "TheTyger" that remains most with the reader is the compelling rhythm. Blake's is a wonderfully lyrical poem.
This lyricism of the poem advances the idea of Blake that God's creative process is the work of an artist moving about as he works. In this poem, the metaphor of the creator as blacksmith with his fire "burning bright" in the tiger as it is forged in the furnace and with the anvil gives form to the dreaded animal who becomes part of the dichotomy of experience and innocence, represented in the fourth stanza with the image of the lamb.
Among the acts of the creator, there is personfication as the "stars threw down their spears,/And water'd heaven with their tears." Then, Blake asks,
Did He smile His work to see?
Did He who made the lamb make thee?
This question may be addressed to Blake's fellow Rationalists who "had hoped for a tame, gentle world guided by kindness and understanding," as Dr. Ed Friedlander states. Instead, they must face the "fearful symmetry" of the tiger, much that is evil and threatening. The poet's opposition of innocence and experience reflects his Doctrine of contraries, a philosophical view that dominated his poetry.
Concerning Blake's, "The Tyger," one doesn't normally talk about which literary devices are the "strongest." I can point out literary devices that are used and are central to the poem, but I can't guarantee that they are the "strongest."
The theme or idea that the same being that made the lamb made the tiger is central to the poem. Blake is dealing with perceptions and the elimination of dichotomies. The lamb and tiger are not created by two different beings, but by the same being. Thus, the being that made them has something of the lamb in him, but also something of the tiger. By extension, then, all of creation, humans included, have the lamb and tiger in them, as well: they are just two sides of every being.
Imagery is also central to the work. You can pick out virtually any line in the poem and find powerful imagery. The image of God hammering out the frame of the tiger on an anvil is a powerful one, located in stanza four.
Finally, allusion plays an important role in the poem. Stanza two includes an allusion to Icarus, who in classic myth attempts to fly to the sun ("...what wings..."). The allusion mixes with the fire imagery, and the idea that the creator forges the tiger in fire, like a blacksmith.
Stanza five contains an allusion to the fall of Satan from heaven (the stars throwing down their spears), and the speaker asks if after the fall of Satan, did the creator look on the tiger and smile.
I'll talk about what I see as the strongest literary element in Wiliam Blake's poem "The Tyger," which is figurative language. Figurative language can be defined as anything said or written that means something beyond the literal meaning of the words that are used. The opening lines of Blake's poem are something that I will never forget precisely because of the intense figurative language:
Tyger! Tyger! burning bright
In the forests of the night,
The tiger is not literally burning, of course, and this metaphor of fire and burning is carried out through the poem and takes on all sorts of associations, including an association with the infernal.
I'll stop here and leave you (or another poster or two) to identify two more important literary elements in the poem.