Malcolm is considered to be honest and noble, like his father. In Act IV scene 3, Macduff meets Malcolm in England where Macduff interrogates Malcolm to see what kind of king he would be and whether he would be worth backing in order to save Scotland. Malcolm turns the table and tests Macduff by telling him all sorts of falsehoods--he is dishonest, greedy, full of lust for women, etc. With each false word, Macduff counters with suggestions to appease the future king's vices and tells Malcolm that he is the rightful heir to the throne and that Macbeth must be stopped at all costs since he is killing their beloved country. Malcolm then admits that none of these vices are true, that he is convinced that Macduff is sincere and not sent by Macbeth to kill him; the two plan the deliverance of Scotland through attacking Macbeth.
In the end of the play, Malcolm is generous, thankful, and full of praise of those who have served him well in the dethroning of Macbeth and the saving of Scotland. We are reminded of the opening of the play where Malcolm's beloved father, Duncan, is performing the same acts. Malcolm appears to be the spitting image of his father and the future of Scotland appears to be in the hands of loving King who will be every bit as loved as Duncan was.
We learn in Act 4, Scene 3 that Malcolm has many excellent qualities, as he tells Macduff that he has never been with a woman, never lied, never desired what was not rightfully his, never broken a commitment or a contractual obligation, yet he does "delight / No less in truth than life:..." (4.3.145-150). Significantly, Malcolm says this immediately after he tests Macduff by telling him how horrible his character is. Perhaps the only seeming flaw apparent in Malcolm is that he fled with his brother from Scotland upon their father's murder, although if they hadn't fled, Macbeth most likely would have had them murdered as well.