"The Lady of Shalott" uses aaabaaab rhyme to establish its dreamlike rhythm and structure, with the final word of each stanza almost always being "Shalott" (on one occasion, the word is "Lancelot"). This repetition alludes to the Matter of Britain tradition from which Tennyson draws his inspiration, a refrain of the sort frequently found in oral-tradition stories and folk tales.
There are many figurative and metaphorical devices within the poem. In the first stanza, we see an example of pathetic fallacy, where nature is described behaving in a way that supports the activity of the story: here, nature is personified and seemingly protecting Shalott, with the "long fields" there to "clothe the wold and meet the sky," and the waterlily and daffodil encircling Shalott. We see this later, where "the little isle is all in'railed." Like the Lady herself, Shalott is encircled, arguably either protected or isolated.
Repetition enforces the Lady's situation: we see the word "weaving" stated over and over to emphasize that this is her only task and consumes her every waking hour. By contrast, Sir Lancelot is compared figuratively to light and stars, signifying his difference from all others; Lancelot's horse's bridle "glitter'd . . . like to some branch of stars we see."