Love sonnets usually have a lover complaining that his mistress is cruel. Drayton's speaker makes a stranger complaint: her eyes are generous, just not to him. They "disperse their rays on every vulgar spirit", while he stays "in the self-same place" in darkness, without "one glance to recompense my merit". The word "merit" gives him away. He isn't hoping for love as a gift. He expects it as payment. The central idea is that understanding goes unrewarded, and that the person who knows most about beauty may suffer most for it. Underneath, the sonnet is an attempt to turn rejection into proof of his own superiority.
The structure is that of an English sonnet: three quatrains and a couplet, rhymed ABAB CDCD EFEF GG. The argument follows those blocks closely. The first quatrain is a grievance put as a question. The second is a single sentence, an extended comparison that begins "So doth the plowman gaze the wand'ring star". The third returns with a second "why" and then a wish, "Would God I were as ignorant as they". The couplet delivers the verdict. The even iambic pentameter helps the speaker sound reasonable, almost like a lawyer building a case, even though what drives the poem is hurt.
The imagery is nearly all light. There are "rays", "darkness", a "glance", "the light", a "star" and "sight". The lady is never described beyond her eyes, so she becomes a source of radiance and nothing more. The ploughman simile cuts both ways. The ploughman looks up at a "wand'ring star", the old term for a planet, and is "contented with the light". He has "never learn'd what constellations are / Beyond the bent of his unknowing sight". "Bent" suggests both inclination and limit. The speaker casts himself as the one who can read the whole sky, yet the simile shows the ignorant man happy and the learned one in the dark. Knowledge has made him more sensitive to what he lacks.
His language is also snobbish. Other admirers are "vulgar", their senses are "gross", and they are "ignorant". Beauty itself is made a servant of convention: she is "custom to obey" and applies herself "so ill" to coarse perception. Judging by this vocabulary, the speaker would rather insult everyone else than admit the simpler explanation, that she just doesn't care for him. A reader can sympathise with his pain and still notice how much of his complaint is vanity.
Small details of sound support the tone. The rhymes "spirit/merit" in lines 2 and 4 end on soft, unstressed syllables, so the sneer trails off. In line 13, "Only compell'd on this poor good to boast", the stress lands hard on the opening word, so the consolation sounds grudging. Then the final line is a run of ten one-syllable words: "Heav'ns are not kind to them that know them most." The slow, even beat gives it the weight of a proverb. "Heav'ns" can mean the sky he has been studying, and perhaps the lady's star-like eyes, or fate itself. The repeated "them… them" turns the line back on itself, as if the speaker were trapped in a circle. His one gain is "this poor good", a boast, and the word "poor" admits that a boast is thin comfort.
What makes the sonnet worth reading is how it reshapes a very familiar situation. Unrequited love becomes a small paradox about knowledge and reward, close to the old idea that ignorance is bliss, but felt from the unhappy side. The tone stays open to argument. It can be read as sincere heartbreak, as self-pity, or as wit that half-mocks its own speaker. Part of the pleasure is deciding how far to trust him. He believes he has exposed an injustice in the heavens, but the poem also lets us see what he cannot: a man so sure of his own merit that he has stopped looking at the person he claims to love.