A feverish speaker stands outside at night and asks the moon for relief. Shelley's «To the Moonbeam» opens with a plea: "leave the shadowy vale, / To bathe this burning brow." Moonlight is imagined as cool water for a hot head. But the request soon turns suspicious. Why is the moonbeam so pale? "Is it to mimic me?" The speaker assumes that anything pale or sorrowful must be copying him. This is the poem's central idea. His suffering is so extreme that nothing in nature, and eventually not even despair itself, can truly match it. The poem never says what caused the grief. It cares only about its size, and about the loneliness of being unable to share it.
The three stanzas move steadily inward. The first looks at the moon, the second at the whole sleeping world, the third at the speaker himself. In the first, the speaker talks himself out of his own jealousy. The moon cannot be copying him, because "thine orb is bright, / And the clouds are light." The scene he describes is almost cheerful, with its "humble wild-flowers" and "star-studded night," and the brightness makes his own darkness harder to bear. The second stanza sharpens the contrast. "Now all is deathy still on earth; / Nature's tired frame reposes". Shelley personifies nature as a body at rest, and "deathy" is a slightly strange coinage that makes ordinary quiet sound like a corpse's. Dawn, which should bring hope, "Flies forth its balmy breath," but for the speaker morning only "Brings but a gloomier night, implants a deadlier thorn." Normal expectations are reversed. Daylight wounds, and the thorn is planted deeper each time the sun rises.
The form helps this along. Each stanza runs on tightly paired rhymes, like "me / be," "morn / forlorn" and "care / despair," then closes on a triple rhyme such as "bright / light / night" or "morn / forlorn / thorn." The effect is of something closing in, a trap snapping shut. The line lengths add to it. Each stanza shrinks into short, clipped lines ("Is it to mimic me? / But that can never be;") and then stretches into one long final line, so that "That at intervals shadow the star-studded night" and "Seem in my breast but joys to the pangs that rankle there" trail out like a sigh or a slowly spreading ache. The rhythm gallops in a loose, rolling way rather than ticking evenly, which suits a mind too agitated to keep time.
The third stanza is the strangest. The speaker turns on himself: "Wretch! Suppress the glare of madness / Struggling in thine haggard eye." He talks about himself as another person, and the archaic "thine" gives the order a stagey, almost theatrical ring. Then the echo comes. In the first stanza the idea of mimicry was a question with a hesitant answer ("never be"). Now it is a boast. Even "Pale Despair's most sickening sigh, / Is but to mimic me; / And this must ever be." "Never" has become "ever," and the speaker has gone from doubting that the moon copies him to claiming that despair is the imitator and he is the original. His ranking of darknesses is almost comically precise. "Care" is a mere "twilight," "despair" is "night," and both "Seem in my breast but joys" beside what "rankle[s] there."
The language is extravagant, with words like "deathy," "rankle," "haggard" and "forlorn," and a modern reader may feel the poem enjoys its own gloom a little too much. Its appeal lies in that excess. It shows a speaker who turns to nature as a confidant, as Romantic poems so often do, and finds that nature cannot answer. The moon is lovely, the dawn is gentle, and neither understands him. What is left is an extreme loneliness, and a hint of unraveling in that "glare of madness." The poem leaves us wondering whether the grief is as unmatched as he insists, or whether competing with despair is itself a sign of how far he has slipped.