Which term describes a composition written in metrical feet forming rhythmical lines?

The term that describes a composition composed in metrical feet and forming rhythmical lines is "poem." Poetry is distinct from prose in that it often adheres to specific structures and rhythms that create musicality and emotion. Metrical feet are the building blocks of rhythm in poetry, where each foot is a specific combination of stressed and unstressed syllables. This characteristic allows poems to evoke feelings and imagery through structured language.

In contrast, a story typically refers to a narrative that may or may not involve rhythm and meter, focusing more on plot and character development. An essay is a more formal piece of writing that explores a specific topic in a structured format, often devoid of the rhythmic qualities of poetry. A narrative generally describes a spoken or written account of connected events but doesn't necessarily conform to the metrically structured nature of a poem. Therefore, "poem" is the most accurate term for a composition characterized by metrical and rhythmical qualities.