Claudius uses one of Shakespeare's most beautiful and most characteristic metaphors when he tells Polonius:
There's something in his soul,
O'er which his melancholy sits on brood,
And I do doubt the hatch and the disclose
Will be some danger . . .
The image is that of a huge dark bird sitting on an egg which will hatch something dangerous, possibly a plot to overthrow or assassinate Claudius. It is characteristic of Shakespeare because he used simple, natural metaphors and similes, unlike some of his university-educated contemporaries who drew on Greek and Latin literature to impress their audiences.
Claudius goes on to explain to Polonius that because of his apprehensions about Hamlet he has decided to send him to England as an ambassador and that hopefully the change of scenes and climates will have a healing influence on Hamlet's troubled mind. Claudius may already be thinking of having Hamlet executed when he reaches England, but naturally he doesn't say anything about that to Polonius.