Shelley fits a whole argument into six lines: everything people fight to own will eventually slip out of their hands, but love will not. The first half of the poem is about loss. "Wealth and dominion", money and political power, the two things most people would call solid, "fade" as soon as they leave our "possession". The second half turns on the word "But" and delivers the claim: love "is among / The things which are immortal."
The imagery of the first two lines is easy to miss. Wealth and power do not simply vanish. They fade "into the mass / Of the great sea of human right and wrong." The picture is of a vast moral ocean in which a fortune or a crown, once let go, dissolves into the general churn of human deeds, some good and some bad. The sea has no memory of who owned what. The poem could have said that riches get spent or that kingdoms fall. Instead it says they lose their identity, which is a quieter and in some ways harsher idea. The things we cling to turn into anonymous water.
The most surprising word in the poem is "misdirected". Shelley could have said that true love, or faithful love, is immortal, which would be the safe, greeting-card version. He admits instead that love can be aimed at the wrong person or the wrong thing, and he still gives it a place among the immortal. The line says only that love is "among" those things, which is modest and precise. Love's worth, the poem implies, does not depend on its being wise or well-placed. The feeling itself outlasts its mistakes.
The form helps the argument along. Every line is a steady ten-syllable iambic line, and the calm, measured rhythm suits a statement presented as plain fact rather than emotional outburst. The rhymes (mass, pass, surpass) occupy alternate lines, with "wrong" and "among" nearly rhyming in between. The pairing of "pass" in line three and "surpass" in line five is especially neat. The same sound describes two opposite fates. Wealth and dominion "must pass", meaning they leave us, while love "surpass[es]" them, meaning it rises above them. Even the rhyme asks us to hear the contrast: to pass is to be lost, but to surpass is to win.
The last line is where the poem's pattern gives way. "All that frail stuff which will be—or which was" is the only line whose final word, "was", has no true rhyme partner. It looks as if it belongs with "mass" and "pass" on the page but sounds different when spoken, so the poem seems to leave its own tidy scheme behind just as it dismisses the things it calls "frail stuff". "Stuff" is a deliberately deflating word, casual and slightly contemptuous, as if crowns and fortunes were clutter. The dash adds a hesitation, and then "will be" and "was" stretch time out in both directions. Everything transient is placed in the future or the past, while love gets the present tense: it "is" and the immortal things "are". The grammar quietly puts love outside the stream of time that carries everything else away.
The title calls the piece a "Fragment", and the Latin "Amor Aeternus" means "eternal love". Whether or not Shelley meant to write more, the six lines read as complete. They begin with loss and end with a rejection of everything that is merely temporary, and nothing feels missing.
What makes the poem worth reading is its compression and its stubborn generosity. In a few lines it measures the usual human ambitions (money, power, ownership) against love and finds them lighter. It does this without pretending that love is always sensible or deserved. A reader can disagree with the claim, but it is hard to miss how deliberately each choice, from the sea to the word "stuff", is made to support it.