Polonius says that Laertes should keep his friends close: "Grapple them to thy soul with hoops of steel;" (I.iii.67). Polonius uses the metaphor "hoops of steel" to describe the strong bonds of friendship. I. A. Richards, an English literary critic, established the two-part interconnection of metaphor as the "tenor" and the "vehicle." The vehicle is the metaphoric language, the figure of speech: "hoops of steel." The vehicle refers back to the literal meaning, the tenor; in this case, it is the strong bonds of friendship. (A good way to remember these terms is that the metaphoric language, the "vehicle," drives away from and back to the literal meaning.)
Polonius personifies "apparel" in line 76: "For the apparel oft proclaims the man." He says that the clothes describe the character or background of he who wears them. But it is the man himself who buys the clothes, possibly with the intention of showing something about himself.
Polonius also personifies 'time' when he says "The time invites you." (I.iii.87) Here, he means that it is time for Laertes to leave. The time does not literally invite him. The situation is right for Laertes to leave. But saying "the time invites" him gives the notion more importance. It's as if to say that time itself is aware that Laertes is about to leave.
There are several literary devices used in this speech. First, we see a metaphor in Polonius' encouragement for Laertes to get going.
The wind sits in the shoulder of your sail,(60)
And you are stay'd for.
So he's telling him it's the proper time for him to be leaving. Next, parallelism defines much of the syntax in the speech. Parallelism is a structural balance of two or more words, phrases, or clauses. Some examples:
Give every man thy ear, but few thy voice;
Take each man's censure, but reserve thy judgment.
Give thy thoughts no tongue,
Nor any unproportion'd thought his act.
Be thou familiar, but by no means vulgar.
Finally, there are some examples of metonymy. Metonymy is the substitution of a word to describe something closely related to it. In his speech, Polonius tells Laertes, "Give every man thy ear, but few thy voice." So, listen to everyone, but be careful in whom you confide.