A brass sky is a sky without rain, and that is the key to Hopkins's sixteen lines. "A brazen heaven" works like a metal lid clamped over the speaker. Prayers rise, strike it, and "fail and scatter all away." The second stanza's "My heaven is brass and iron my earth" closely echoes a curse in Deuteronomy, where the sky overhead turns to brass and the ground underfoot to iron. Hopkins takes that image of divine withholding and turns it inward. The drought is in the speaker's own spiritual life.
The poem is about prayer that no longer feels like prayer. The speaker is "unclean and seeming unforgiven," and the word "seeming" matters, because it leaves a small gap between how things feel and how they might be. The same gap opens in the line "I reckon precedents of love, / But feel the long success of sin." To "reckon" is to tot up evidence like a bookkeeper, and the speaker can still do that sum. He knows, as a matter of record, that love has been shown before. But the evidence stays on paper, while what he feels is sin winning, and winning for a long time. Head and heart disagree, and the poem will not pretend otherwise.
The form is plain and controlled, and that makes the despair sound more severe. Each stanza has eight lines rhyming ABAB, in a steady four-beat line that mostly keeps to an iambic pulse. Hopkins is famous for dense, bending, newly coined language, but here the vocabulary is mostly short and ordinary, and the plainness reads like an honest report. The rhymes carry meaning too. "Above" is paired with "love," so love sits out of reach overhead. "Win" is paired with "sin": the entrance he "cannot … win" rhymes with the thing that keeps winning against him. The word "away" is used twice, first when prayers "scatter all away" and again when the dearth is something "praying fails to do away." Prayers vanish, and the drought stays.
The second stanza moves from sky to ground, and its imagery is a chain of cause and effect. A brass heaven gives no rain, so there is "dearth." Without water, clay hardens, and "iron is mingled with my clay." The speaker's own substance has been toughened and stiffened. Tears would normally soften it, but the poem stumbles over the thought: "Nor tears, nor tears this clay uncouth / Could mould, if any tears there were." The doubled "nor tears" sounds like someone reaching for a reflex that no longer works. The conditional "if any tears there were" admits that even the grief has dried up. "Uncouth" suggests clay that is rough and unshaped, waiting for a hand to work it, and "mould" hints that someone else might do the shaping if only the clay were soft enough.
Everything has gone wrong, yet the last two lines turn on a single idea: "A warfare of my lips in truth, / Battling with God, is now my prayer." The speaker has stopped calling his prayers prayers, but he now redefines the word. If gentle, tearful, trusting prayer is impossible, then a struggle will count. The weapons are only "lips," which suggests words forced out without much feeling behind them, but the phrase "in truth" claims that this is the honest version. The poem ends on the very word it doubted in line four ("My prayers I scarcely call to pray"), and the speaker takes it back on harder terms. Battling with God is still a way of addressing God.
That is why the poem matters. Religious verse often offers consolation, but this poem stays in the dry place and says what it is like there. It also suggests that faith can survive as an argument, an act of stubbornness, a refusal to stop speaking to a silent sky. The metal and clay images are heavy and physical, so the despair feels like a condition of the body as well as of the mind. A reader who has never prayed can still recognise the experience of reaching for a feeling that will not come, and of finding that the reaching itself is the only thing left.