All poems whose titles end with songs, lines, songs, etc. They are all ancient poems. For example, Go and Stay, Liang and Song at Four o'clock in the Midnight. And many of them are named after the theme or the first word, such as Shu Dao Nan, Fang Shu, Gongwu Crossing the River, Luoziban, Shangxie and so on. Most of the poems before Wei and Jin Dynasties were ancient poems except Chu Ci.
Classical poetry is an ancient style, as opposed to metrical poetry. Generally, the rhyme is not strict, so you can rhyme. The number of words is also uncertain, and four, five, six and seven miscellaneous words can be used. For example, Li Bai's "Into the Wine".