The Iliad is an example of what is known as "oral-formulaic epic." Rather than originally having been composed in written form by a single individual, it is an accumulation of traditional materials concerning the Trojan War, perhaps shaped by a single "monumental poet" from earlier materials. It displays many characteristics of formulaic composition.
One of the most obvious elements of this in the Greek text (something reproduced more or less faithfully by various translators) is the presence of epic epithets or formulae, repeated phrases that fill out a particular metrical portion of a line. These can be noun or verb phrases, such as "the laughing Aphrodite" or "beating the sea with their oars." These phrases, repeated over the entire epic, irrespective of relevance to context (the phrase "laughing Aphrodite" is used even when Aphrodite is crying), not only facilitate oral improvisational composition but help to create the strongly delineated flat characters, defined by a limited set of characteristics, typical of oral epics. Formulae exist on the level of scene as well as lines, such as "donning armor" and combat scenes.
Another typical epic characteristic is that The Iliad is highly agonistic, not just in terms of the overall story arc, which is about a war, but also in terms of the way people compete to be the best ("aristos," somewhat equivalent to an MVP in modern sports) in the day's fighting.
Another characteristic of epic we see in The Iliad is that it is agglutinative. It creates its effects not by analysis but by heaping up details. A typical battle, for example, is shaped using the rhetorical structure known as gradatio or climax, in which a hero kills a series of opponents, beginning with weaker nameless ones, progressing to stronger named ones, and finally engaging in a climactic battle with a powerful opponent.