我是個假詩人

就古典詩歌來講，英文講究meter和form。form有sonnet，ballad等。meter也不同，通常是輕音／重音 入 at last （at unstressed，last stressed）。in a sonnet，每行都應該五個這樣的unit，一共10個音節(similar to 5 alternate 平仄 pair in Chinese) 。當然還要押韻。英文poem（古典）是看syllable數，not number of words in a line. Some of what I wrote (sonnets) followed the rules, some didn't.
As for haiku, originally it required 575, where each number indicates the number of syllables (not words) in the corresponding line. Later they relaxed the requirement (in terms of syllable count). Right looks like there is a grammatical change or something, but I never delved into it. Classic poems are much more difficult to write.
Of course there are many nonclassic poems that are just as good such as the raven (from Poe). Whitman might be the first who broke the ground in free verse. Certainly there are music and rhythm in those.
ha