Does Malcolm become king at the end of the play?

The correct answer to this question is TRUE.

With his brother Donalbain, Malcolm quickly ascertains the danger of remaining in Scotland and flees the country (Act II, Scene 3). By the time he reappears, in Act IV, Scene 3, he has won the support of Edward the Confessor (king of England), he has mobilized troops under Northumberland and Siward, and he is "every inch a king." In the final scene of the play, Malcolm is presented as the future king.

His use of the phrase "by the grace of Grace" indicates the importance that he attaches to the service of good and reminds the audience of his direct descent from one who ruled by divine right, as opposed to Macbeth, who usurped the throne. Like his father Duncan, Malcolm is the representative of order.