When considering the effects of the use repetition in Thomas's most famous poem, the alternating last lines of each stanza are obvious examples whose dire imperatives create the poem's urgent, incantatory tone. The poet reveals in the final stanza that his reflections on the bitter final moments of various types of men amount to evidence in the case the poet is arguing to his dying father to resist the encroaching blackness as long as the old man can. Beyond just imploring his father to hold on, the repeated refrains at the end of the stanzas also function as a prayerful talisman whose exhortations to life and light are imbued with spiritual or psychic energy to reanimate or reinvigorate the perishable body.

Just as significant as the repeated final lines of each stanza, the first lines of the middle three stanzas repetition of different qualities of "men": the "wise," "good" and "wild." All of these types are alike in recognizing the insufficiency of a human lifespan to do, or say, or make all of the things that a person realizes are left undone when it is finally too late. Before the final stanza, when it becomes clear that the poem is specifically addressed to the poet's father, the poet introduces and supports the point about the universality of the dying regrets he wishes his father to be spared from.

The speaker of this poem utilizes repetition from the first stanza; the final line of that stanza implores his father to "rage, rage" against the process of dying. Repeating a word in quick succession is a literary technique called epizeuxis. The effect of this type of repetition is to establish a vehement sense of urgency. "Rage" is a particularly strong verb to use here; it connotes a sense of violence and anger. Thus, the speaker begs his father to bolster up the energy for a battle against death, refusing to simply slip gently away from life.

The final word in each stanza also exemplifies repetition, alternating between night and light. Night symbolizes death in this poem, and light represents life. Through this alternating repetition, life and death are inextricably linked to each other. The road of life must inevitably lead to death; however, the speaker issues a repeated command, saying, "Do not go gentle into that good night," beseeching his father to continue living. Though the speaker realizes that a metaphorical night must eventually come, he asks his father to hold on to the light for as long as possible.

The repetition of these symbols and phrases convey the depth of the speaker's love for his father. Unwilling to imagine a world without his father in it, the speaker is even willing to accept the "curse" of his father—as long as it conjures up enough strength for him to fight fiercely. The repetition helps to establish a tone of intimacy as the speaker begs his father not to leave him.

Dylan Thomas repeats alternating lines at the end of each stanza; they are "Rage, rage against the dying of the light" and "Do not go gentle into that good night."

Both lines are imperatives that the poem's speaker is delivering to his father; this is revealed in the poem's final quatrain after a series of five tercets. The repetitions of these lines add emphasis and urgency to the idea that his father must not passively accept his demise; he should, rather, battle to the last moments of his existence. The speaker seems to believe that life is precious and should not be given up without a fight. Moreover, the speaker creates a catalog of men (with "men" being another word that is repeated as a point of emphasis) who did not "go gentle" as a point of comparison and a behavior for his father to emulate. He expresses the wish that his father will also "burn and rave" as his last moments approach.

The repetition of the first and third lines of the poem impress the reader with the speaker's relative desperation that his father fight against death (we learn the narrator of the poem is speaking to his or her father in line 16). It sounds as though the speaker is trying to persuade his or her father that, although continuing to live might be painful or difficult, resisting death is the best thing, the right thing, to do. The speaker repeats these lines in the context of describing all different kinds of men—wise men, good men, wild men, and serious men (or men who are very near death, since "Grave" has two potential meanings here)—and all the different reasons that they choose to stay in "the light." This seems to be an attempt to convince the father that no one else goes "gentle into that good night," so neither should he.