How to distinguish quatrains from metrical poems?

Quatrains and metrical poems are two different genres of modern poetry, which can be distinguished from the following two aspects:

First, the number of sentences is different. There are four quatrains, which are divided into five quatrains and seven quatrains, with 20 quatrains and 28 quatrains. The number of sentences in a metrical poem is 8, which is divided into five laws and seven laws, with 40 words in five laws and 56 words in seven laws.

Second, the requirements for confrontation are different. Some quatrains only have the first two sentences, some only have the last two sentences, some are all the first two sentences, and some are not at all. The first couplet and the last couplet of a metrical poem are not necessarily couplets, but the parallel couplet and the neck couplet must be couplets.