goes along with the idea of this poem being a mock epic. It takes a very trivial event (cutting hair) and treats it like an epic event such as the adventure inThe Odyssey: treating a haircut like it was the crime of the century. The idea of women cutting their hair was frowned upon in Pope's time, but it would still be an exaggeration to call it rape. 

The poem uses a lot of tropes and devices particular to epics, but often in mocking ways: sprites/spirits, the suiting of armor (Belinda putting on makeup), games, and a banquet. What makes it even more exaggerated is the lofty speech and that the gods (sylphs and spirits) try to stop the rape/cutting. It is an exaggeration that the cutting of Belinda's hair is so reprehensible as to require gods to intervene. As the Baron attempts to cut the hair, the sylphs try and stop him: 

The peer now spreads the glitt'ring forfex wide, 
T' enclose the lock; now joins it, to divide. 
Ev'n then, before the fatal engine closed,
A wretched Sylph too fondly interposed; 
Fate urged the shears, and cut the Sylph in twain
(But airy substance soon unites again)
The meeting points the sacred hair dissever
From the fair head, forever and forever! (Canto 3, 147-54)

The background to "The Rape of the Lock" is a trifling dispute between two families of English Catholic aristocrats over the unauthorized cutting—the "rape" of the title—of a lock of hair. The lock in question belonged to a society lady called Arabella Fermor, whose suitor, Lord Petre, was responsible for carrying out the infamous deed. This generated a minor scandal at the time, though Pope clearly found it a source of considerable amusement, not to mention poetic inspiration.

As much as anything else, "The Rape of the Lock" is a satire on English upper-class society and how it is so self-regarding that it makes mountains out of the most trifling of molehills. This grotesque exaggeration of a trivial event lends itself to Pope's mock-heroic treatment. For Pope to deal with such a piffling affair in the style of Homer or Virgil allows the reader to see just how vain, shallow, and self-absorbed the English aristocracy could often be. They are presented by Pope's unflattering portrait as so rich, privileged, and cut off from the outside world that they no longer have any sense of proportion, of what's really important in life.

Pope was asked to write "The Rape of the Lock" after a seemingly trivial incident blew up into a fight between the Fermor family and the family of Lord Petre. Lord Petre had become enamored of Arabella Fermor and cut off a lock of her hair without permission, starting the quarrel. You can find out more about this background in the eNotes link below. 

Homer's Illiad also is a background story for this mock heroic, which pokes fun at a minor incident of hair cutting by exaggerating it to epic proportions. Using the Illiad as a frame highlights the differences between real problems, such a genuine war, and losing a lock of hair.  For instance, the taking of Helen of Troy, a serious incident in the Illiad, becomes the frame for the taking of the lock of hair, making the uproar over the lock all the more ridiculous in comparison. A description of the famous warrior Achilles' shield becomes the description of a petticoat. Contemporary audiences, well-versed in classical literature, would have understood and appreciated the humor in this parody of the Illiad. 

These lines come from the first canto of Alexander Pope's mock epic The Rape of the Lock. They appear in the fourth stanza. In previous stanzas, the speaker introduces a “dire offence” about to be committed against the hapless Belinda. He appeals to his Muse to inspire him and then asks some questions. What, he wonders could make a “well-bred lord t' assault a gentle belle,” and what could make “a gentle belle reject a lord?”

The scene then turns to Belinda's bedroom. She is still asleep although the sun is long up, and it is already noon. Her “guardian sylph” is making her stay asleep, for he wants to warn her in a dream that something horrible is about to happen. The fourth stanza begins the sylph's speech.

This sylph, named Ariel, begins by telling Belinda that a “thousand bright inhabitants of air” care for her. Belinda should be aware of her importance to these spirits, to this “light militia of the lower sky.” Belinda must turn her attention to the things above and believe in her guardians. Ariel then goes on to explain that these spirits were once women, and they are sent to care for other women. There are many different kinds of these spirits, everything from salamanders to nymphs to gnomes to sylphs, all with different functions. These spirits guide young ladies in their pursuits and their courtships.

Later in the passage, Ariel introduces themselves and tries to give Belinda a warning. This sylph has seen “In the clear mirror of thy ruling star” the imminence of “some dread event” set for that very day. Belinda must beware of men.

Of course, we know that this “dread event” is nothing greater than a gentleman cutting off one of Belinda's prized locks of hair. Pope, however, uses Ariel's speech to set the stage for this event, to introduce the supernatural characters of this mock epic, and to increase the ironic drama of the poem. We readers now know that there is some “danger” about (although since this is a mock epic, there is plenty of irony about, too). Epics generally have supernatural beings at work within them, yet here Pope makes them quite silly (on purpose, of course). Still, the drama is set, as satiric as it is, and we are ready to watch it unfold over the course of the poem.