Acrostic poems do not have to rhyme. The main characteristic of an acrostic poem is that the first letter of each line spells out a word or message when read vertically. This unique structure allows for creative expression without the necessity of rhyme. While some poets might choose to incorporate rhyme for rhythmic effect or aesthetic reasons, it is entirely optional. The focus of an acrostic poem is more on the theme conveyed by the vertical word rather than the sound of the words themselves.