People shouldn't keep or make enemies
Act 1, Scene 1
The feud between the Montagues and the Capulets has caused a big fight in one of the streets of Verona. Lord Montague goes to join the fight but Lady Montague holds him back. Lord Montague tries to get Lady Montague to let go of him so that he can go fight: "Thou villain Capulet!-Hold me not, let me go" (996). This shows that people shouldn't keep or make enemies because the fight has no point and no winner, so the two families are not only putting their own lives at risk, they're putting the lives of innocent bystanders at risk.
Act 3, Scene 1
Tybalt and Mercutio have just gotten in a fight and Tybalt killed Mercutio. In anger, Romeo chases after Tybalt and ends up killing him. Now, Lord Montague must convince the Prince that Romeo shouldn't be killed: "Not Romeo, Prince; he was Mercutio's friend; His fault concludes but what the law should end, The life of Tybalt" (1051). Because of the feud, Romeo, Lord and Lady Montague's only son, is banished from Verona. Now, since Romeo is banished, Lord and Lady Montague won't be able to see him much, putting an enormous amount of stress on them, which results in Lady Montague dying.
Act 5, Scene 3
After Romeo and Juliet commit suicide, Lord Montague talks of constructing a statue of Juliet: "There shall no figure at such rate be set As that of true and faithful Juliet" (1102). It takes the death of his only son for Lord Montague to finally realize that Juliet and the Capulets shouldn't have been treated as enemies and that they shouldn't be anymore. Lord Montague then goes on to make amends with Lord Capulet, that's when they go on to talk about constructing gold statues of the other one's child.
Theme: Act 5, Scene 3
The feud has just caused the deaths of Romeo and Juliet. The Prince then scorns Lord Capulet and Montague because the deaths could've been avoided if they didn't hate each other: "Capulet, Montague, See what a scourge is lain upon your hate, That heaven finds means to kill your joys with love!" (1101). This shows that people shouldn't make or keep enemies because the feud between the Capulets and Montagues kept Romeo and Juliet apart, which, when they took matters into their own hands, resulted in both of them commiting suicide.