What is the term for a long narrative poem that features heroes and heroic deeds significant to a culture?

The term that refers to a long narrative poem that showcases heroes and their significant deeds within a particular culture is "epic." Epics are characterized by grand themes and a narrative style that often includes an array of elements such as gods, supernatural occurrences, and a journey or quest that is of great importance to the culture from which the epic originates. They reflect the values, beliefs, and historical experiences of a society, often celebrating national or cultural identity through the heroic actions of their protagonists. Examples of well-known epics include "The Iliad" and "The Odyssey" from ancient Greece, as well as "Beowulf" from Anglo-Saxon literature.

The other terms you might encounter serve different purposes: a lyric typically expresses personal emotions or thoughts rather than telling a story, a ballad usually narrates a short story, often in a simple and musical form, and an ode is a formal address to a subject, often depicting admiration or emotional reflection but not necessarily narrative in nature.