Milton's Paradise Lost is a long, narrative poem told in a serious manner, using elevated language, featuring characters of a high position. All of these characteristics suggest the work is an epic poem.
The piece also begins in medias res (Latin for "in the middle of things") as Homer's epic poems do. The speaker also invokes, following the custom of the Greeks, help from the supernatural to inspire and guide him in the telling of the tale.
The manner and language of the poem, as well as the request for help, are revealed in the opening of the poem:
Of man's first disobedience, and the fruit
Of that forbidden tree, whose mortal taste
Brought death into the world, and all our woe,
With loss of Eden, till one greater Man
Restore us, and regain the blissful seat,
Sing Heavenly Muse, that on the secret top
Of Oreb, or of Sinai, didst inspire
That shepherd [Moses], who first taught the chosen seed,
In the beginning how the Heavens and Earth
Rose out of Chaos:....I thence
Invoke thy aid to my adventurous song,
That with no middle flight intends to soar
Above the Aonian mount, while it pursues
Things unattempted yet in prose or rhyme.
The serious tone and elevated language are obvious (the speaker is not just writing a narrative, he is attempting to do something never before done in literature, for instance), but what may be most notable, or at least most interesing, is the speaker's connection of the Muses from Greek myth to the Holy Spirit of the Bible. The speaker fuses the Greek and the Christian, or, as some would phrase it, the Pagan with the Christian. In preparing to tell the epic tale of Satan's fall from heaven, the speaker equates the Muses and the Holy Spirit.