What is a meter in poetry and how does it work?

Read the following poem carefully, and then answer the questions that follow. sonnet 73 by william shakespeare that time of year thou mayst in me behold when yellow leaves, or none, or few, do hang upon those boughs which shake against the cold, bare ruin'd choirs, where late the sweet birds sang. in me thou seest the twilight of such day as after sunset fadeth in the west, which by and by black night doth take away, death's second self, that seals up all in rest. in me thou see'st the glowing of such fire that on the ashes of his youth doth lie, as the death-bed whereon it must expire consumed with that which it was nourish'd by. this thou perceivest, which makes thy love more strong, to love that well which thou must leave ere long. comprehension what seasonal images do you see in this poem? how do these images contribute to the poem's tone of loss and sadness?