Also, various songs are not to be taken seriously. That is not always the artist's intention.
Okay, let's get that clear. The term "fuck" is also a verb, meaning to have sex with, and is not only a noun "sexual intercourse." Therefore, the person from Black Eyed Peas is saying "Don't mess with my heart."
Some think 'phunk' means 'f..k', altho officially there is not verified meaning to this made up word. Anyways, 'f..k' colloquially means 'sexual intercourse', so to say, or sing 'Dont sexual intercourse with my heart' makes no sense.' And when listening to songs I do like the words to make sense.