Every literary genre is characterized by a number of conventions that have become attached to it over the course of time. Readers who are knowledgeable about a genre expect to encounter these conventions when reading a work in that genre. For instance, readers of war novels expect to have some battle scenes described in them; if a work purporting to be a war novel did not have any battle scene descriptions, readers would probably wonder about the competence of the writer of that novel. Similarly, a police movie that failed to include the obligatory car chase would probably also fail to do well at the box office. For many modern literary works, readers grow up with the conventions and do not even think about them, but for works without much currency in the modern world, readers often have to learn the conventions before the works will begin to make sense.

    The epic, as fashioned by Homer and honed by Virgil and many later epic poets, is a genre possessing a number of conventions, most of which have to be present in a long narrative poem if it is to be accepted as an epic. Poets may violate the expectation of readers for these conventions, but they incur a certain risk by doing so. Great epic poets often refashion conventions for their own purposes, as Milton does in Paradise Lost, but most epic poets adhere rigidly to the accepted conventions, so knowledge of these conventions will improve understanding of an epic.

    Here is a partial list of conventions associated with the great epic poems of the Western tradition:

1. The epic begins in medias res (i.e., in the middle of things).

2. The beginning of the epic specifies the epic theme (i.e., the wanderings of Odysseus).

3. The beginning of the epic contains an invocation to the Muse for inspiration.

4. God(s) (and sometimes goddesses) watch over the action and sometimes assist the hero and others in the action; these supernatural beings are referred to as the "epic machinery."

5. Humans offer sacrifices to god (the gods) to gain support; these sacrifices usually, but not always, are in the form of grilled cattle; when 100 cattle are sacrificed, it is called a "hecatomb."

6. The epic hero(ine) embodies the qualities most esteemed in his/her culture.

7. The hero’s weapon(s) has (have) a history that is related (i.e., the shield of Achilles).

8. Epic similes are used to describe and define important action and events.

9. Catalogues of important items will be listed (i.e., the ships of the Greek fleet in The Iliad).

10. Epic games (physical contests) are described.

11. Epic battles are described and great deeds performed.

12. A visit to the Underworld takes place.

13. A minstrel will sing of great deeds.

14. The hero(ine) will often have a faithful companion.