Tennyson uses multiple literary devices in "The Lady of Shalott," including simile, imagery, metaphor, and symbolism.
In part three of the poem, Tennyson describes the details of Lancelot's armor and horse:
"The gemmy bridle glitter'd free,
Like to some branch of stars we see
Hung in the golden Galaxy." (82-84)
Tennyson uses a simile to compare the glitter of the horse's bridle to the stars at night. This simile also incorporates imagery, creating visual image in the readers' mind. The celestial imagery continues later in part three in the third stanza as Lancelot journeys to Camelot:
Burn'd like one burning flame together,
As he rode down to Camelot.
As often thro' the purple night,
Below the starry clusters bright,
Some bearded meteor, trailing light,
Moves over still Shalott. (94-99)
The comparison of Lancelot to a meteor is significant, because the metaphor suggests that the knight travels a fixed course, with no room for variation, like a meteor. With all his flash and brilliance, Lancelot cannot change his course or stop for the Lady of Shalott.
Tennyson also employs symbolism with his use of the mirror that shows "shadows of the world" in part two (46). A curse binds the Lady to weave, and her only view of the world is the mirror. The mirror symbolizes the false promise of the outside world; it shows the reality of what happens beyond the tower, but is only an illusion. When the lady finally leaves her weaving for Lancelot; the mirror "crack'd from side to side," signifying that her fragile connection to the real world has been broken by the curse.