Two of the main resources available to the poet writing in meter are the tension between the line and the sentence (this is available to the poet writing in free verse, but what poet and critic John Hollander calls the metrical contract of, say, the iambic pentameter line foregrounds the reader’s expectations of the shape of the line and thus also foregrounds violations of those expectations and deviations from that shape), and the tension between the meter and the speech rhythm (this is a resource that is largely lost to the poet writing in free verse). Shakespeare's well-known sonnet 129 exemplifies the ways in which the tension between metrical pattern and speech rhythm can be a source of energy and a mode of making meaning.
Th’ expense of spirit in a waste of shame
Is lust in action; and, till action, lust
Is perjured, murderous, bloody, full of blame,
Savage, extreme, rude, cruel, not to trust,
Enjoyed no sooner but despisèd straight,
Past reason hunted, and no sooner had
Past reason hated as a swallowed bait
On purpose laid to make the taker mad.
Mad in pursuit, and in possession so;
Had, having, and in quest to have, extreme;
A bliss in proof, and proved, a very woe,
Before a joy proposed; behind, a dream.
All this the world well knows, yet none knows well
To shun the heaven that leads men to this hell.
There is a great deal of question about how much the sequence of the sonnets reflects Shakespeare’s own arrangement, though it’s clear that the first 126 are addressed to or about the beautiful young man (let’s not forget, as many people seem to want to do, that the great majority of these poems are about one man’s love for another man), sonnets 127 through 152 are about the so-called “Dark Lady,” the speaker’s mistress, with whom the beloved young man has an affair, and sonnets 152-154 have no connection to the rest of sequence. The sonnets about or addressed to the young man present a much more idealized view of love than do the so-called “Dark Lady” sonnets, which are both more sexual and more cynical (as in the famous sonnet 138, “When my mistress swears that she is made of truth,” in which the poet and his mistress get to lie with each other because they lie to each other).
If the order of the sonnets as we have them reflects Shakespeare’s own arrangement, it’s interesting that Sonnet 130, “My mistress’ eyes are nothing like the sun,” a parody of the conventions of Petrarchan love poetry (her teeth are like pearls, her hair is like spun gold, her cheeks are like roses, her voice is like music, etc.) and specifically of the blazon, in which the beloved is as it were anatomized, broken down into her component parts which are praised and compared to various precious objects (I’ve always thought that there was something dehumanizing about the blazon), immediately follows this sonnet about the pains and dangers of sexual desire. It’s as if the speaker has resigned himself to his state of sexual enthrallment: he sees that his mistress is not perfect, but also knows that no real woman is, and that the perfect image of the Petrarchan beloved is not only unattainable (the Petrarchan lover’s desire is never satisfied) but also unreal. A real woman is better than an idealized goddess, not least because one can actually have her. (Pardon any implication of sexism in the use of the language of possession; I am writing from the then-contemporary perspective.)
But back to the tension between metrical pattern and speech rhythm. In this sonnet, we are immersed from the first line in the speaker’s agitated, disturbed state of mind. He is trapped, and unhappy about his entrapment, and his language reflects that. Though they can certainly be scanned as iambic pentameter, the first three lines of the sonnet have four heavy stresses (and the third line is loaded with stop plosives, “p” and “b”s); the fourth, made up largely of monosyllables (“cruel” has to be read disyllabically to make the meter work, but that’s not how we would naturally read it) has five such heavy stresses. The second quatrain’s lines scan more easily, but the stresses are still very heavy, highlighting the emphatic nature of the utterance. And the first line of the third quatrain line starts with a trochee (one would hardly pronounce it “Mad IN”—a preposition almost never takes a stress in speech, unless one is emphasizing the difference, in this case, between being in and being out of something). The line after that begins with a spondee, the comma giving equal stress to “Had” and the first syllable of “having”—again, the emphatic nature of the speaker’s utterance is foregrounded. The last two lines of the third quatrain scan more easily, but throughout the poem both the heavy punctuation and the piling-up of short phrases serve to break up and agitate the metrical pattern, constantly forcing the reader to stop and start again. The predominance of monosyllables and disyllables (only two words, “despisèd” and “possession,” are longer than two syllables; though “murderous” would normally be trisyllabic, for the purposes of the meter its second syllable is elided, so it’s pronounced “murd’rous”) also reinforces the heavy stresses, since shorter words take stronger stresses than longer words. (Even in a word with more than one stress, the stresses are not equal; there is a primary stress and one or more secondary stresses.) Strong stresses, in turn, slow down a line.
All this—the predominance of short, heavily stressed words, the heavy punctuation, the metrical substitution—works to slow down and break up the meter and to act out the speaker’s agitated state of mind. Through these three quatrains, the speaker has been immersed in his dilemma, caught up in the coils of lust as in the coils of a boa constrictor, and his language has reflected that. In the final couplet, the sonnet’s volte or turn, however, he steps back. In the standard rhetorical structure of the sonnet, the first portion lays out a problem, dilemma, or a situation, and the second portion presents, if not a solution to the problem, then at least a response to it. Here, in the concluding couplet we have a turn of mind; the situation has not changed, but the speaker’s relationship to it has. Having expatiated on the experience of lust in action from within that experience, he steps back and comments on that state. He is no longer in the midst of the experience, but now looks at it from the outside: “All this [that I have said about lust] the world well knows.” At this point, the rhythm evens out. There is only one comma in the final couplet, and the meter scans perfectly. The greater rhythmic poise enacts the speaker’s greater mental calm. He has moved out of the midst of entrapment, at least temporarily, and can now look on it with a colder eye: we all know these things, and yet we do them anyway. The poem opens up into a larger comment on human nature, and on the inability of our knowledge to control our actions when faced with overpowering primal urges. One can almost see the speaker shaking his head with a rueful smile.
This leads perfectly into the next sonnet: my mistress is no goddess, but she is a woman and she is mine. He is resigned, but he is also healthily realistic.