When Claudius asks Hamlet why he's still in a "cloudy mood", Hamlet responds with a pun on the words sun/son, while at the same time alluding to a common expression of the time: to be "in the sunshine of the king's favor." By becoming Claudius' step-son, Hamlet is closer in kinship to him and receives more attention than he wants. These lines both establish Hamlet's facility with language and set the tone of tension between the two men.