To be exact, it is the earliest epic in the history of English literature. In fact, the earliest literary forms of most ancient civilizations in the world are epics, such as Ramayana in India or Homer in Greece. Beowulf, which first appeared in Britain, tells the history of national development in an epic way, which is the practice of many nationalities in the world.
As for poetry, all primitive literary forms of mankind are poetry, even the most "alternative" China is no exception. It is generally believed that after the existence of literary consciousness, the form of verse is the easiest to spread orally.