This poem is a villanelle, a type of French pastoral lyric not often found in English poetry until the late nineteenth century. It derives from peasant life, originally being a type of round sung on farms, then developed by French poets of the sixteenth and seventeenth century into its present form. For Dylan Thomas, its strictly disciplined rhyme scheme and verse format provided the framework through which he could express both a brilliant character analysis of his father and an ambivalent expression of his love toward him.

In its standardized format, the poem consists of five tercets and a quatrain, rhymed aba, aba, aba, aba, aba, abaa. In addition, the first and third lines of the opening tercet alternate as a refrain to the four following verses and become the last two lines of the concluding quatrain. Such a demanding restriction requires poetic ingenuity to maintain a meaningful expression. Here the form provides the poet with a suitable framework for his four characteristic types—wise, good, wild, and grave men—and enables him to equate these types with his father’s character.

Dylan Thomas’s poetry is consistently rich in imagery and metaphorical language. He seems almost to be an apotheosis of Welsh poetic creativity. The poetic spirit pervades his grammatical and figurative speech. The opening line, which also serves as the title of the work, contains the euphemistic metonymy for death, “that good night”—that is, a word associated with death (“night”), but termed “good” in order to overcome its negative connotations. The line also uses the adjective “gentle” instead of the adverb “gently,” as would be customary. As a result, one finds the poet describing the man rather than the manner in which he must move, providing a tighter relationship to the poem as a whole.

The phrase “old age” may be thought of as personification, but it may also be interpreted as a metonymy (substitution) for his father. “Burn and rave” are intense expressions of the defiant stand the poet advocates against “the close of day,” here a metaphor for death, as is “dying of the light” in the next line. “Dark is right” in the second stanza represents a terse acknowledgment of the intellectual recognition of death’s inevitability, but the awareness that his father’s words had “forked no lightning” is a rich metaphor for failure to influence the powerful but brilliant forces within society.

In the next stanza, the poet turns to imagery of the sea: The “frail deeds” dancing in a green bay present numerous levels of interpretation. On the level of the imagery itself, one glimpses a happy dance taking place in a surrealistic body of green water. On another level, the green bay seems to be a metaphorical representation of life itself, green frequently representing the vital and fertile elements of human existence. That frail deeds have failed to enter into the vital life stream seems to be the poet’s judgment that his father, although a good man, had never experienced fully the joys that human life offers.

In the next tercet, singing “the sun in flight” returns one to metonymy, where Thomas conceives his father as recognizing the creative genius capable of some glorious poetic vision but stifling it, “grieving it.” Such wild men must acknowledge the need to defy death. “Blind eyes” blazing “like meteors” in the fifth stanza introduces the first simile of the poem and maintains the celestial vision of the tercet before it.

In the concluding quatrain, the reader comes at last to the apostrophe directly addressing the poet’s absent father, which confirms that he is the individual toward whom the poem is directed. The ambiguity of the poet’s feelings toward his father is emphasized by the paradoxical second line of the stanza, “Curse, bless, me now,” as well as by the “sad height” from which his father can view the poet. The height is metaphorical, implying the closeness to death and to vision of the elderly man; the sadness in the lines derives from his father’s personal failure to fulfill his own high goals.

“Do Not Go Gentle into That Good Night” is a poem reflecting Dylan Thomas’s complex attitude toward his father, David John Thomas. The elder Thomas had been a schoolmaster in the grammar school that his son attended and had instilled in the young poet a love for the English of William Shakespeare and the Bible. He had himself written poems in his childhood and seemed to desire to create in his son the poet he had never succeeded in becoming. He had also become the model for the oracular reading voice that Thomas adopted for his own poetry.

That the younger Thomas held his father in high esteem appears clearly in the poem. The adjectives that the poet uses to characterize him are “wise,” “good,” “wild,” and “grave.” The first two are clearly laudatory, although in each case the virtue is mixed with disappointment that it had no wider effect on society. The wildness, however, adds a dimension unseen in the first two qualities: Its influence has somehow interfered with the poetic inspiration that it clearly comprehends. “Wild men” discover they “grieved” the “sun in flight.” This statement is ambiguous; it could mean that the father interfered with the flights of genius in himself or in others, including Dylan. It could also refer to the poet himself, whose wildness led to dissipation responsible for his own manifold problems—by psychological transfer, he may be applying this to his father.

His father’s gravity, however, is hardly characteristic of the son. Although the term suggests dignity worthy of respect, it connotes here a somberness that has been blind to human joy, something the poet had clearly experienced, as many of his poems indicate.

In the final stanza, the poet wants to wring from his father on his “sad height” a curse-blessing, somewhat in the mode of the biblical Jacob as he stole his birthright from Esau. In this case, the curse is the suffering rage the father must experience as he glimpses the glory of what might have been had he fulfilled his own promise; to some degree, he has transferred the rage to his son in the form of insecurity about his own achievement. The blessing is the genius he provided to his son—genius which he had himself fulfilled only vicariously—and supported with his strong sense of language and its power.

This nineteen-line lyric consists of five tercets (groupings of three lines) and a concluding quatrain (a four-line stanza). Addressed to the poet’s father, it gives him advice about how he ought to die.

In the first tercet, Dylan Thomas tells his father to defy death. After the first line, however, he generalizes about old age, declaring that it should “burn and rave” against dying. This message is contrary to the usual association of a peaceful dying with good character and a virtuous life. Such an association, for example is found in John Donne’s “A Valediction: Forbidding Mourning” (1633), or in Leo Tolstoy’s The Death of Ivan Ilyich (1886).

In the second tercet, the poet begins a series of characterizations of the types of men who rage against death. Here it is wise men who defy death. Their defiance assumes a somewhat ambiguous character: They know that death must come, that indeed, according to the poet, it “is right,” but they have not, in their lives, caused any great stir among humankind (“their words had forked no lightning”). Consequently they must now express that defiance which they previously withheld.

The third tercet deals with good men who cry that their small accomplishments might have shown brilliantly in a more dynamic setting. The poet asserts that they too should rage against death. The last opportunity for finding that setting has passed. The goodness of these men might have shown much more to advantage had they been able to live among responsive and appreciative neighbors.

The fourth tercet advises those who perceived and gloried in the light of inspiration and the development of genius in others and in themselves, but whose actions impeded its progress, to defy death. The poet calls them “wild men” because they comprehended the wildness that has long been associated with poets.

Thomas’s last category, grave men who, near death, perceive again too late that they have not expressed their capacity for brightness and lightheartedness in life, must also rage against dying. Even blind eyes, he says, can “blaze like meteors.” In a concluding quatrain, the poet asks his father to reward him and acknowledge his petition by showing the fierce tears of his rage against dying.

Dylan Thomas is often perceived as a primitive poet, partly due to his legendary reputation as a hard-drinking, wild-living Welshman. This image leads many to believe that his poems miraculously appeared on the page, fully formed from his passionate nature. In reality, the opposite is true. Thomas's poetry is meticulously crafted, often employing complex structures.

"Do Not Go Gentle into That Good Night" is a finely structured villanelle, consisting of five tercets, which are units of three lines of verse, followed by a quatrain, a unit of four lines of verse. The poem's opening line, which is the first line of the first stanza, also concludes the second and fourth tercets. The third and final line of the first tercet serves as the concluding line in the third and fifth stanzas, and these lines also become the last two lines of the quatrain.

The poem's entire rhyme scheme revolves around the words ending the first two lines, "night" and "day." The first and third lines in each stanza rhyme with "night," while each second line rhymes with "day." These words are more than mere rhymes; they provide the contrasting imagery that forms the poem's core. Thomas also employs internal rhyme to create a smooth, melodic flow in his poetry. His use of alliteration, with repeated initial sounds, is evident in words like "go" and "good" in the first line, and "blind" and "blaze" in line 14. Assonance, or the repetition of vowel sounds, is illustrated by "caught" and "sang" in line 10. In line 17, "curse" and "bless" exemplify half-rhyme, another technique Thomas frequently uses.

Some critics describe the poem's meter as primarily iambic pentameter, where each line consists of five segments of two syllables, with the first syllable unstressed and the second stressed, as in the word "above." "Pentameter" indicates five such segments per line. However, Thomas's poetry often defies conventional metric analysis. Thus, many critics prefer to analyze his poetry by the number of syllables in each line, rather than by metric feet. Consequently, "Do Not Go Gentle into That Good Night" can also be described as decasyllabic, featuring ten syllables per line.