T. S. Eliot is considered one of the most important poets in the modernist movement. Many aspects of his poetry influenced subsequent forms of modernism in literature. His critical essays, especially "Tradition and the Individual Talent" were also influential.
One of the important innovations of Eliot's verse was borrowing the concept of free verse ("vers libre") from the French symbolists and implementing an equivalent in English. Unlike some late twentieth century free verse, Eliot's version maintains a ghost or scaffolding of traditional forms, so that the reader gets a sense of the writer interrogating the poetic tradition in which he is situated, both appropriating and rejecting it at the same time, in a gesture that follows his critical understanding of the way the modern poet interacts with his predecessors.
Another important modernist theme the Eliot develops is that of the fragment, as expressed in the ending of "The Wasteland":
Poi s'ascose nel foco che gli affina
Quando fiam uti chelidon - O swallow swallow
Le Prince d'Aquitaine à la tour abolie
These fragments I have shored against my ruins
Why then Ile fit you. Hieronymo's mad againe.
Datta. Dayadhvam. Damyata.
What makes this ending so striking is that it contains four different languages, and material from five different previous works. The fragments are not explained or placed in coherent logical order, but starkly juxtaposed in a way that suggests the chaos into which modern society falls (for Eliot in part due to the decline of religion and monarchy) and how it leads to a "'dissociation of sensibility".
Many poets found Eliot's success in writing this new style of verse liberating. The method of highly individuated references, including proper names, is also seen in Pound, the imagists, and many later poets, such as John Berryman.
Eliot also worked for many years as a poetry editor at Faber & Faber, one of the leading publisher of poetry in England, and thus has an immediate personal influence on modern poetry, encouraging many younger poets and helping them develop in their craft.