"My mistress' eyes"- simile

"My mistress' eyes are nothing like the sun."  This is an example of a simile.  This compares the mistress' eyes to the sun.  This line came from the poem "My mistress' eyes" by William Shakespeare.  This is a very interesting poem, but it was a little difficult for me to understand.  "Black wires grow on her head."  When the speaker says this, it makes it seem that he finds his mistress as unattractive.  It also proves that her hair is black.  "With false compare."  When I read this line, I felt that it meant that he did not truly love her.  He is just using her for sex, since she is a mistress.