Tennyson uses language appropriate for a hero--an adventurer, soldier, leader of men. Some of the power of the poem results from lists and parallel structure. One such example occurs when Ulysses characterizes the citizens of Ithaca as a "savage race/That hoard, and sleep, and feed, and know not me." Or, when he calls his mariners "Souls that have toiled, and wrought, and thought with me-- (44-45) Perhaps even more effective is the last line in which Ulysses encourages his fellow mariners to "To strive, to seek, to find, and not to yield." (70) Other such lists and parallelisms can be found throughout the poem.
Another effective technique is the frequent use of contrasts in the same line: "Though much is taken, much abides" (65); 'The thunder and the sunshine," (47); and "made weak by time and fate, but strong in will" (69).
You might also examine the metaphors for death ("touch the Happy Isles"), living life fully ("To sail beyond the sunset") , and merely existing ("To rust unburnished").