There is a great deal to be said about the symbolism surrounding Cupid and how his symbolism perfectly portrays Romeo in the play.
For starters, Cupid is recognized as the god of love, more specifically of erotic desire and passion. He is the son of Venus, goddess of love. He was often portrayed as a boy having wings, carrying a bow and arrow, and being blindfolded. His wings symbolize the fact that lovers who are in a state of passionate, erotic love are also known to be extremely flighty, meaning "given to flights of fancy," meaning that they are driven by what's in their imaginations rather than what is reality (Random House Dictionary). The word flighty can also refer to the fact that lovers tend to change their minds suddenly; they are very fickle. Therefore, Cupid's wings show love as being poorly grounded. In addition, Cupid is portrayed as either a nearly teenaged boy or as a younger chubby boy to portray the youthful side of passionate love. Erotic love is very naive, and the young have a tendency to be very foolish and even irrational. Also, Cupid carries a bow and arrow to symbolize how love can hurt the heart. Finally, Cupid is also portrayed as being blindfolded because erotic love does not see clearly or rationally. Erotic love sees reality as pure fantasy and is even somewhat arbitrary.
Mercutio's reference to Cupid in Act 1, Scene 2, as he teases Romeo for being swept away by his amorous feelings, perfectly portrays Romeo, making it a perfect reference for the play. Just as Cupid symbolizes, Romeo certainly is taken to flights of fancy. He begins the play being completely caught up in his love for Rosaline, even though he really has no firmer reason for being in love with her other than that she is beautiful, showing us that he has allowed his imagination to govern his sense of reality. Not only that, Romeo proves to be flighty, as Cupid symbolizes, because he also proves to be very fickle. It takes him no time at all to switch from being in love with Rosaline to being in love with Juliet. Friar Laurence characterizes Romeo's fickle nature best in his lines:
Holy Saint Francis! What a change is here!
Is Rosaline, that thou didst love so dear,
So soon forsaken? Young men's love then lies
Not truly in their hearts, but in their eyes. (II.iii.66-69)
Not only is Romeo very fickle, just as Cupid symbolizes, he is also very young, naive, and irrational. We especially see his irrationality portrayed in his response to Rosaline's rejection. It is perfectly irrational for Romeo to stay up all night long, night after night, as he has been doing. Even Friar Laurence argues that Romeo is actually far too young and naive to really understand what true love is.
Hence, we see that Cupid is not only the perfect symbol of erotic love but also the perfect symbol to portray Romeo, making Cupid the perfect symbol for the play.
Cupid is so appropriate to the play as its central focus is oung love. His present state of being blindfolded signifies the blinding nature of their passionate love and provides an insight (or explanation) into their often rash, unconsidered actions.