Rhythm is a critical element in poetry, and good poems generally have a clear rhythm and meter. Free-verse poetry may change rhythm periodically or avoid traditional notions of rhythm but still ensure that the overall sound of the poem appropriately conveys its meaning. Bad poetry, by contrast, may have an incoherent or jarring rhythm or might adopt a rhythm that is not appropriate to its subject matter. In other cases, bad poetry may sacrifice rhythm entirely in an attempt to ensure that words rhyme. Many good poems follow classic rhythm schemes such as the iambic pentameter in Shakespeare's "Sonnet 73," which reads in part, "That time of year thou mayst in me behold." A bad rewrite of this poem might read something like, "That moment of year that you could see here in me." Here, the number of syllables before each emphasized syllable varies and the rhythm does not follow any standard rhythm scheme.
Not all poetry rhymes, but rhyme scheme can play a major role in bad poetry. Oftentimes, bad poems focus on ensuring that words rhyme rather than conveying sensory imagery or depth. Bad poets might replace precise language with imprecise language in an effort to make poems rhyme. For example, "My dog/ is a hog/ I wish he lived in a bog" sacrifices meaning, precise language and depth in favor of rhyming. Good poems, by contrast, have a rhyme scheme that makes sense, that does not interrupt the rhythm and that still allows for precision and variation in language. In William Ernest Henley's "Invictus," for example, the rhyme scheme adds to the meaning of the poem without forcing awkward language: "It matters not how strait the gate / How charged with punishments the scroll / I am the master of my fate / I am the captain of my soul."
Poetry isn't just a sentence with a clear rhyme or rhythm scheme. Instead, poetry aims to convey depth of feeling or philosophical concepts by taking advantage of the added meaning that can be found through rhyme and rhythm. While good poetry might address a mundane topic, it rarely simply describes the topic. Instead, it attempts to find deeper meaning or convey lessons. Bad poetry, however, might simply describe an everyday object and rhyme. A bad poem might read, "My cat / is on the mat / he looks like that." In "Invictus," by contrast, the importance of the poem's message is conveyed in the first stanza, which ends with the following lines: "I thank whatever gods may be / for my unconquerable soul."
Poetry thrives on sensory imagery that allows the reader to hear, see, smell, taste or touch the subject matter. In Henry Wadsworth Longfellow's "A Tale of Arcadie," the vision of a forest is clearly brought to life with the lines, "This is the forest primeval. The murmuring pines and the hemlocks." Poetry also frequently plays on a reader's emotions and encourages her to develop new emotional reactions to a common occurrence. Some poetry attempts to describe complex emotional experiences. Bad poetry, by contrast, rarely makes good use of imagery and may be completely inept at making the reader feel that she is experiencing the same thing as the poet.