Shakespeare' "Sonnet 20" is known also as "A woman's face with nature's own hand painted".

Watching the title I expect the sonnet to be about a woman whose face is really attractive. "Nature's own hand painted" gives an idea of something perfect, created by Nature. 

As regards layout, the poem is arranged in a single stanza of fourteen lines. The stanza is split in two parts, with a full stop at the end of line eight. The poet decided to split his poem in two parts, because each part plays a different role. First eight lines are descriptive about the beauty of a face. In the second part, the poet focuses the attention on himself with terms such as "me", "mine", "my purpose". The function of the second part is to analyse the importance that the picture of the woman has for the poet. 

Moving on to the connotative analysis,the poem has many words that belong to the semantic field of feelings such as "passion" and "pleasure". The rhyme scheme of the poem is ABAB-CDCD-EFEF-GG. In the first line there'is a personification, because Nature is identified in a painter.

The sonnet is linked to Oscar Wilde's "The picture of Dorian Gray". Both deal with a portrait, and with the themes of beauty, youth and pleasure. Even if in the sonnet there is a contraddiction between the two genders, as the poet doesn't really express if beauty is something feminine or masculine.