What language and tone is used in Shakespeare's "Sonnet 55"?

Shakespeare's language and tone in Sonnet 55 are, to an extent, more distant and austere than one finds in many of the sonnets. One notices that the speaker addresses the beloved, the Fair Youth, with "you" instead of "thou." Although the shift in the standard second-person pronouns was already occurring in the seventeenth century, "you" was still a more formal, respectful, and less intimate manner of address.
The speaker's tone clearly shows his awe of the object of his love and praise. The comparison is made with matters of state—princes and war—and with mythology in the reference to Mars, the god of war. And yet, at the end, in the final couplet, one can see a softening of the language and a humbler tone, given the reference to the Last Judgment. It is as if the speaker has yielded his elevated ranking of the Fair Youth in deference to God's ranking.
The principal idea expressed in Sonnet 55, I would argue, is that poetry and art in general can confer immortality upon an individual in a way that the material world cannot. It's interesting to compare this poem with a very well-known sonnet by another English writer, Edmund Spenser. One of the most famous sonnets in Spenser's Amoretti begins "One day I wrote her name upon the strand, / But came the waves and washed it away." The speaker is then chided by his beloved for vainly believing he can "immortalize" her. He counters that it's not the physical depiction of her name but rather his verse, his art, that will make the idea of her live forever. Shakespeare's theme is similar to Spenser's: "marble and gilded monuments," though stronger and more durable, are analogous to a name written in the sand. The material world will pass away, but art, "this powerful rhyme," is the means by which the one being addressed (the so-called Fair Youth) "shall shine more bright" than stone until Judgment Day.