The crown is always a visual symbol of a monarch's power but in Henry IV Part 2 it comes to mean even more. Let's take a look at a few significant moments where the crown comes into play. First, we want to think about the moment when King Henry IV refers to his crown when he tells us how exhausted he has become. When he says "Uneasy lies the head that wears a crown" (3.1.1), he makes it sound as if the crown is so heavy and uncomfortable that it prevents him from getting any sleep. Of course, Henry doesn't actually wear his crown to bed. The "crown" is a metaphor for the king's weighty responsibilities and the burden that comes with his power. In other words, the pressures of kingship keep the guy awake at night.
When Prince Hal visits his father and blames "the crown" for Henry's illness, he implies something similar to what King Henry says.
Why doth the crown lie there upon his pillow,
Being so troublesome a bedfellow?
O polish'd perturbation! golden care!
That keep'st the ports of slumber open wide
To many a watchful night! (4.5.5)
Prince Hal addresses the object as though it's literally responsible for his father's exhaustion. He calls it a "troublesome bedfellow" that keeps his father awake at night. Here too, Hal is using the crown as a metaphor for the burden of kingship.
Soon after, Hal takes the crown (prematurely) when he mistakenly thinks his father has died. When King Henry awakens from his nap and figures out what's happened, Hal's possession of the crown seems to be evidence that Hal wants his father dead. "Thy life did manifest thou loved'st me not," says Henry, "And thou wilt have me die assured of it" (4.5.4). For King Henry, Hal's possession of the crown represents a lifetime of Hal's disobedience, selfish desire for power, and hatred of his father.
Of course, we know that Henry fails to recognize that his son cares for him deeply but, we also wonder if there isn't just a bit of truth in Henry's claim. (Shakespeare will later explore a similar situation in King Lear, where Gloucester's son, Edmund, wants to kill his father.) When Hal returns the crown and father and son reconcile, the crown is not just a symbol of political power or responsibility, but of the complicated father-son relationship that builds tension throughout the both parts of Henry IV. If you're interested in exploring this further, check out our discussions of "Family" and "Power."