The use of first-person narrators is common in much poetry, from Shakespeare’s sonnets to Coleridge’s The Rime of the Ancient Mariner. When the poem is narrative in character, that is when the speaker is telling a story to a listener (rather than emoting or describing inner thoughts), the effect is “endistancing”. These stories are removed by at least one person from the immediate narrator. In this case, where the subject is reputation versus direct evidence of greatness, the endistancing helps make the point that there is always an element of exaggeration, and even falsehood, in one’s reputation. Ozymandias the historical figure is a perfect example: everything we know about the Egyptian king and his accomplishments comes from documents of self-praise or forced loyalty, stories of his deeds carved on monoliths, etc. Shelley is saying “Reputation is a story someone made up.” The transience and fragility of such reputation is of course depicted in this poem, this “story” passed down from narrator to narrator, and (now, as a much anthologized poem) passed down to more generations. So the first-person telling augments the theme.
The reader "hears" at least three narrative voices in this sonnet. The first belongs to the narrator who says, "I met a traveler. . . "; the second belongs to the traveler, who narrates what he encountered on his travels; and the third is the voice of Ozymandias, whose words have been chiseled into the base of the stone sculpture of himself. Reading between the lines, the reader hears a fourth voice; one that communicates non verbally. And this, is the voice of the sculptor, who records his contempt for his tyrannical master, by capturing his unattractive and unpleasant expression :".. . frown and wrinkled lip and sneer of cold command" in stone, and records it for posterity. The words of Ozymandias, filtered through these several narrators, become ironic because their impact on the reader is the opposite of what Ozymandias would have intended in the first place. Ozymandias' intention was to record his greatness for posterity and have the onlooker gaze at his image in awe. Instead, the onlooker is made to recognize the transient nature of worldly power and the absurdity of taking pride in such power. Another theme of the poem is one that is found in many Shakespearean sonnets - that immortality can be achieved through Art. Ozymandias is immortal, not because of his works, but because the sculptor has made him so. Thus the first person narrative voices, serve to filter the original message and intention of Ozymandias, and present them in a totally ironic and different manner.