When Romeo first appears in act 1, scene 1 of William Shakespeare's Romeo and Juliet, he tells his friend, Benvolio, that he's in love with a woman whose name he won't reveal. Romeo says only, "I do love a woman" (1.1.206) and tells Benvolio that the woman has vowed to live a chaste life, which devastates Romeo and casts him into utter, lovesick despair.
Romeo asks Benvolio what he can do to stop thinking about the woman.
BENVOLIO. By giving liberty unto thine eyes.
Examine other beauties (1.1.229–230).
As luck would have it, in act 1, scene 2 Romeo is presented with exactly that opportunity. Romeo is still lamenting his unrequited love for a woman when the two friends meet a servant from the Capulet household who's been tasked with inviting people to the Capulets' feast.
The servant has a list of people invited to the feast, but the servant can't read. He asks Romeo and Benvolio if they can read, which they can, and Romeo reads the list of invitees, which just happens to include Rosaline.
Even though the feast is at the home of the Capulets, the Montagues' (Romeo's family) greatest rivals, Benvolio suggests to Romeo that they go to the feast so that Romeo can look at other women and get his mind off Rosaline (whose name Benvolio has somehow learned).
BENVOLIO. Compare her face with some that I shall show,
And I will make thee think thy swan a crow (1.2.90–91).
Romeo scoffs at the idea that there will by any woman at the feast who can compare to Rosaline, but he reluctantly agrees to go the feast simply to be able to look at Rosaline.
ROMEO. I'll go along, no such sight to be shown,
But to rejoice in splendour of my own (1.2.105–106).
Nothing is ever that easy for Romeo, of course, even going to a party to look at beautiful women.
In act 1, scene 4, on the way to the Capulets' feast, Romeo tells Mercutio and Benvolio that he has a "soul of lead" (1.4.16) and a burden of love that weighs heavily on him. Romeo says, "I dreamt a dream to-night" (1.4.53), but before he can explain the dream, Mercutio launches into his famous, if lengthy, "Queen Mab" speech (1.4.58–100).
When Mercutio finally finishes talking, Romeo explains, somewhat overdramatically, why he's fearful of going to the party. At the same time, Romeo foreshadows the end of the play.
ROMEO. 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, clos'd in my breast,
By some vile forfeit of untimely death (1.4.113-118).
Oddly, after making such a dire prediction, Romeo's mood suddenly changes. He decides to trust his life to fate and heads off to the party with his friends.
ROMEO. But He, that hath the steerage of my course,
Direct my sail! On, lusty gentlemen! (1.4.119–120)
As for Benvolio's reason for wanting to go the Capulets' feast, he doesn't say. It might be that he enjoys a good party and free food, or he wants to look at beautiful women himself, or he hopes to be proven right in taking his friend Romeo to the feast to lighten his "leaden soul" and ease the burden of his heavy, lovesick heart.