has turned to "age's steepy night" (5), and all the beauty that he possesses now will fade away so that he loses it completely (6–8). In preparation for this, the speaker fortifies himself against the "cruel knife" of age (9–10), and he vows that he will never allow himself to forget his love's beauty (11–12). In the end, he claims that his love's beauty will always continue to live in these lines he has written and that the verse will keep his love "still green": youthful and beautiful forever (13–14).

The poet personifies time, giving it hands and the ability to purposefully crush and wear down a person as they age (2). He also uses a metaphor to compare youth to the morning and age to night (4–5). He compares his love to a king via another metaphor (6). He employs still more metaphors to compare youth to the season of spring (8) and aging to a "cruel knife" that cuts out our memories (10).

This is a rather standard sonnet topic: a speaker claiming that he will immortalize a lover's beauty in verse and, in so doing, keep it alive forever so that the beauty will never fade or die. However, this poem is somewhat unusual in that it does not employ apostrophe—when the speaker directly addresses someone who is absent or dead as though they could respond. In this sonnet, the speaker does not speak directly to his beloved.

"Sonnet 63" is part of the "Fair Youth" sequence, the first 126 of Shakespeare's sonnets, and, like several others in the sequence, is concerned with the theme of youth preserved in ink when it has died in reality. The poem begins with the word "Against": the poet is actually establishing from the start that his poem is intended as a sort of charm or proof "against" the ravages of time he then goes on to list.

The poem guards against the possibility of his love really becoming "as I am now," when his "youthful morn / Hath travelled on to age's sleepy night." At the moment, the beloved youth is "king" of many beauties, "the treasure of his spring," which will inevitably fall into decline. The poet appreciates that physical beauty cannot survive the cuts of "age's cruel knife."

What the poet expresses in this sonnet, however, is that while age can cut into physical beauty, it cannot "cut from memory / My sweet love's beauty." Memory is proof against physical decline, and through the commission of that beauty to writing, the poet ensures it remains in the memories even of those who never saw it in reality. His beauty "shall in these black lines be seen / And they shall live, and he in them still green"—that is, green as he was in the "spring" of his life, even when it is long past.

Sonnet 63 is about a favorite theme for sonneteers, that of poetry immortalizing beauty and love. It begins with the poet saying that in preparation for the time when "my love shall be" as old as he himself is at the time of writing, he shall immortalize him "in these black lines" and keep "my lover's life" still "green," or youthful, with "sweet love's beauty."

Sonnet 63 is in iambic pentameter with two voltas, or change in topic within the subject of the sonnet. The first 12 lines are 3 quatrains with a rhyme scheme of abab cdcd efef. The last two lines are an ending rhyming couplet with the rhyme scheme gg. This is what came to be the standard English, or Shakespearean, sonnet form. It is not in the original Petrarchan sonnet form. The voltas (i.e., thought turns) are at lines 5 and 9. At 5, he turns from Time to the journey that will cause his love's kingly "beauties" to vanish "out of sight" and steal the youthful "treasure of his spring."

At 9, he turns to protesting "Against confounding age's cruel knife," asserting his love shall be "never cut from memory." The couplet explains that "His beauty shall in these black lines be seen, / ... / and he in them still green."

That [Age] shall never cut from memory
My sweet love's beauty, though my lover's life:

[Couplet]
His beauty shall in these black lines be seen,
And they shall live, and he in them still green.

Shakespeare's subject in Sonnet 63 is the transience of life, the power of memory, and the permanence of poetry.

In the first four-and-a-half lines, for example, the poet prepares himself for the point at which old age begins to change his lover:

Against my love shall be, as I am now,/With Time's injurious hand crush'd and o'er-worn;/When hours have drain'd his blood and fill'd his brow/With lines and wrinkles

First, the poet describes himself as a victim of time, which has worn him out, and he is developing a defense against the time when his lover is also "crush'd and o'er-worn."  Shakespeare skilfully uses balanced language to create images in his reader's mind: drained his blood/filled his brow with wrinkles.  As usual with Shakespeare, he takes the abstract concept of aging and makes it real with imagery.

Shakespeare uses the metaphor of age as a journey in the second half of line four and line five when he notes that his lover's "youthful morn/Hath travell'd on to age's steepy night," a journey that ends with his lover's physical beauties disappearing (ll. 5-6)--literally "stealing" youth ("his spring") from his lover.

Beginning with line nine, Shakespeare discusses the measures he will take to blunt

. . . age's cruel knife,/That he shall never cut from memory/My sweet love's beauty, though my lover's life. . . .

In other words, even when his lover is dead, the poet's memory will prevail and conserve his love's youthful beauty.

The couplet (ll. 13-14) makes the argument that the poem--"these black lines"--will live on, and in lving on, will always present the poet's lover "in them still green," that is, always youthful and beautiful.  In essence, then, the lover lives in the memory, which is then recorded by the poem, and the poem is what remains.