English sonnets generally possess an element of love or romance, but as has already been stated, modern sonnets can deal with social issues, politics, nature, and even death of a loved one. Be that as it may, English sonnets are phrased in iambic pentameter, which is a line of verse with five metrical feet, each consisting of one short (or unstressed) syllable followed by one long (or stressed) syllable. The sing-song effect generated by English sonnets is by reason of this very meter.
Villanelles are not easy to compose; for while on the one hand, they have strict rules pertaining to the repetition of verses, on the other hand, they are required to follow a rhyme scheme. There are only two repeating rhymes throughout, which means that each of the tercets uses the rhyme scheme ABA while the quatrain uses the rhyme scheme ABAA.