What happens
The Nurse goes up to wake the bride and finds her cold and still. Her shrieks bring the whole house running. Capulet, Lady Capulet, and Paris arrive to a scene of horror — the wedding has become a funeral in an instant, and each pours out grief over Juliet's body. Friar Lawrence, who knows the truth, steps in to steady them: he tells them she is past their tears, now in a better place, and that they should dry their eyes and carry her to the family tomb with the rosemary and wedding clothes still on her. The mourning party leaves, and a small comic exchange between the household musicians and the servant Peter closes the scene.
Why it matters
The grief is real and the audience knows it is misplaced, which puts us in an uncomfortable double position. We cannot fully mourn with the Capulets because we know she is alive — yet we can see the plan slipping, because she has been laid in the tomb a day early and Romeo still does not know.
The Friar's calm is its own kind of horror. He stands over a family destroyed by a death he engineered and counsels patience, even piety. The play lets you feel how far his good intentions have carried him into deception, soothing the very grief he is secretly causing.
The odd comic bit with the musicians at the end jars on purpose. Shakespeare refuses a clean tragic curtain; life's pettiness keeps intruding. It also lets the audience breathe before the final act, where the tomb the Capulets have just filled becomes the place everyone dies.