Night in Shakespeare's plays, such as Hamlet and Macbeth, often symbolizes evil, the uncanny, or danger. However, in Romeo and Juliet the night is "blessed" and the lovers are protected by the "cloak of night." Night becomes a place of safety within this play because the feud between the two families exists in the day-lit streets. The positive depiction of the night shows us how backwards and dangerous these character's reality is.
Here, Romeo references his own name as the deadly weapon that kills his love. Notice how Romeo's name has been used throughout the play. Juliet tries to remove the importance from it in order to love him; Benvolio places it on him and marks him as Mercutio's avenger; Romeo now refuses to speak it because it is deadly. Romeo's name becomes a symbol that underscores the arc of the main plot.
"Hie hence, be gone, away!..."See in text(Act III - Scene V)
Though Romeo is teasing her in the preceding line, Juliet takes Romeo's threat of death seriously and stops pretending it is not morning. Notice how the theme of light and dark is used to symbolize the shift in Romeo and Juliet's relationship: while the night was a safe and playful space, the day is a serious and grim place where death exists.
A nightingale is a bird that sings at night while a lark sings at dawn. Here, Juliet calls the bird outside a nightingale in order to prolong the last night she has with Romeo. The nightingale symbolizes the night time in which they can be together, the lark symbolizes the dawn in which he must escape to Mantua.