This is an ironic passage: on their way to the party, Romeo insists to Mercutio and Benvolio that he is too heavy-hearted with unrequited love to participate happily in this party. Romeo believes he is too depressed and too deeply in love with Rosaline to enjoy himself. Benvolio talked Romeo into attending this party as a way to cure his lovesickness by showing him how many other pretty girls are in Verona. Still, Romeo doesn't believe he could possibly be interested.

In this passage, Romeo expresses a sense of foreboding about this party, saying he feels fated for an untimely death. He mentions having had a dream but is diverted from telling it by Mercutio's long discourse on Queen Mab and dreaming. 

Since Romeo does not expect to find love at this party, we can assume that his sense of dread arises from fear that Capulets will kill him in a fight when they realize he, a Montague, crashed a Capulet party. The irony arises from the fact that Romeo will fall in love and it will be that, not exposure as a Montague at the party, that is ultimately responsible for his death. The feud will lead to his death, but not in the way he thinks.

The sense of fear and foreboding Romeo experiences is an example of foreshadowing: he is fated to die and this path will "bitterly begin" at the party. His lines here have a poetic cadence, emphasizing their importance. "Mind misgives" and "bitterly begin" are forms of alliteration. The soft rhyme in "breast" and "death" further adds to the poetic cadence. Shakespeare also mentions stars, a recurrent image in the play. Romeo speaks of a "consequence yet hanging in the stars," by which he means he has a sense of fateful foreboding, but star imagery will also permeate the way Romeo and Juliet will refer to each other, so Shakespeare, characteristically, is using double entendre to indicate that both fate and Romeo's soon-to-be "star" Juliet will determine what is to come. 

Most of Romeo's comment ("I fear, too early: for my mind misgives/ Some consequence yet hanging in the stars/ Shall bitterly begin his fearful date/ With this night's revels and expire the term/ Of a despised life closed in my breast/ By some vile forfeit of untimely death" [I.iv.112-117]) is an example of foreshadowing. Romeo suspects that this is the start of something that will end in "untimely death," and, of course, he is correct. In the next scene, Romeo will meet Juliet and then learn that she is a Capulet and thus the daughter of his father's enemy. He will be doomed because he loves her at first sight but neither can change the fact that they are members of warring families.

In these lines, Shakespeare also includes metaphor and personification. "Some consequence" is personified when Romeo refers to it as "his." Romeo's description of what "consequence" will do "being his fearful date ... and expire the term of a despised life") could also be considered an example of metaphor as it is a non-literal way to say that he suspects that the consequences of his actions will lead to his death.

At the end of these lines -- "But He, that hath the steerage of my course,/ Direct my sail! on lusty gentlemen!" (118-119) -- Shakespeare continues to use both personification and metaphor (two techniques that fall under the larger umbrella term "figurative language"). The metaphor here compares Romeo himself to a ship and the "He" (the former "some consequence" again) is in charge of steering the ship. What is significant here is that Romeo sees himself as not in control of his own fate. He feels that the course of his life will be determined by outside forces. This sentiment connects to one of the themes of this tragedy: that the ongoing Capulet/Montague feud has doomed the two young lovers. 

Romeo is responding here to Benvolio's comment that they are going to be too late for the Capulet party.

Romeo is saying that he is scared that they won't be too late, but too early as in they shouldn't go at all. He believes this because he has a gut feeling (his mind misgiving him) that due to going to this party, something bad is going to happen (the consequence).

This is foreshadowing the tragic events that will unfold due to the love between Romeo and Juliet. The love is a consequence of having met Juliet at this party which then leads to the deaths of many including Romeo and Juliet themselves.