what stands out to you and why? What questions do you have?

Shall I compare thee to a summer’s day?
Thou art more lovely and more temperate:
Rough winds do shake the darling buds of May,
And summer’s lease hath all too short a date:
Sometime too hot the eye of heaven shines,
And often is his gold complexion dimmed;
And every fair from fair sometime declines,
By chance, or nature’s changing course, untrimmed:
But thy eternal summer shall not fade,
Nor lose possession of that fair thou ow’st;
Nor shall Death brag thou wander’st in his shade
When in eternal lines to time thou grow’st:
So long as men can breathe or eyes can see,
So long lives this, and this gives life to thee.

The thing that stands out to me is the formality and tone of the poem. The author uses very unique language, he's comparing something or someone to a summer's day.

When I read "And often is his gold complexion dimmed" I think he's talking about the sun, I think he might be comparing life to a summer's day. He says "every fair from fair sometime declines" I think that means that with more time, something gets worse.

But no matter how bad it gets, you should stay the way you are and don't let death get the best of you.

Questions:

What exactly is he comparing to a summer's day?

What is the meaning of "thou"?

Why is the poem in the tone that it is?