What are the strict requirements of ancient metrical poems?

Metric poetry, also known as old-style poetry, is a unique kind of poetry in ancient poetry, which refers to poetry works written according to certain sentence patterns and phonological rules. No matter in China or abroad, metrical poetry is a poetic style formed in ancient times. In Chinese classical poetry, it mainly refers to modern poetry with strict rhythm, such as five-character poems, seven-character poems, five-character poems and seven-character poems formed in the Tang Dynasty. Every poem has strict rules on antithesis, evenness and rhyme, and even the number of words in each poem is strictly limited.