In the first Act of this play it is clear that the themes of love and violence are inextricably intertwined. I will briefly look at the first scene and then Act I scene v to show how these themes are juxtaposed to show their opposition.
The play begins with a brawl between the two houses of Montague and Capulet. It is worth considering the speed at which the conflict escalates: the henchman are engaging in witty, sexual dialogue, which links violence and sex, and then before they know it are involved in a brawl that rapidly grows until the heads of both households are present and involved. Benvolio (whose name literally means "good will") tries to stop the conflict but is drawn into the fray by fiery Tybalt, which perhaps foreshadows the way that violence is so powerful in this play that it draws in characters in spite of their best intentions - for example, Romeo killing Tybalt later on in the play. This is a scene that is captured brilliantly in the Baz Lurman version of the play, when Romeo kills Tybalt whilst at the same time showing that he is forced into this situation. Violence begets violence in this play with no conceivable escape.
Act I scene v is the scene we have all been waiting for - Romeo and Juliet meet and fall instantly and hopelessly in love with each other at the party at the Capulet house. However, amidst this blossoming of love, the ever threat of violence is present, as Tybalt recognises the voice of Romeo and goes to get his sword, and is only prevented from doing so by his uncle. It is highly significant that at the same time that Romeo and Juliet get together, Tybalt's rage is provoked against Romeo, triggering events which will eventually result in Romeo's banishment from Verona. How tragic that in the very happiness that initiates the start of their relationship should also lie the seeds of their future sadness, but this is a key technique of Shakespeare and of course why this play is one of his most famous and well-known tragedies.