"Sonnet 60" uses alliteration to bring its images and ideas to life. The clearest alliteration comes in the poem's second quatrain, where the speaker tells the story of a human life in miniature—showing how quickly the prime of life starts to fade. Youth, the speaker says:
Crawls to maturity, wherewith being crown'd,
Crooked eclipses 'gainst his glory fight,
And Time that gave doth now his gift confound.
Note the repetition of /cr/ sounds above, which link the stages of life: the "crawl" of youth, the "crown" of maturity, and the "crooked eclipses" of old age. The alliteration creates the sense of life moving ceaselessly forward, each phase "changing place with that which goes before"—just as "waves" and "minutes" do in the poem's first quatrain.
The sharp /c/ sound then gets echoed by "eclipses" (which counts alliterative because the shared sound falls at the start of a stressed beat, "eclipses") and "confound." All this alliteration makes the story sound all the more powerful and inescapable, much like the passage of time itself.
The other alliterative sound in these lines pits those aforementioned "crooked eclipses" (again, the passage of time and dawning of old age) "'gainst" the brief "glory" of youth. These hard /g/ sounds feel aggressive, suggesting a futile struggle against the mighty force of time. The alliteration of "gift" and "gave" in the very next line has the same effect.
Finally, the alliteration in line 10 is deliberately show-offy: "beauty's brow." The poem makes the point that beauty is short-lived and soon taken away by time. The sonic play in the phrase "beauty's brow" seems like a vain attempt by the poem itself to hang onto the beauty being described.