Robert Frost sticked to the traditional poetry forms such as blank verses or sonnets. However, he did experiments on various modification to the traditional meters. In his poetry, sentence sound, which is Frost`s poetic principle and which is based on speaking voice, affects on the meter. The modifications to the meter sometimes strengthen the meanings and sometimes it imply irony, satire, or paradox. Additional syllables, flexible feet, modified rhymes in his sonnets, intended rhyme patterns in his blank verses could suggest something more than the words on the paper mean, so careful attention is needed to understand his poetry perfectly.