What do you think Malcolm's perspective on being king is in Macbeth?

Although Malcolm doesn't actually speak when King Duncan, his father, names him the Prince of Cumberland (the heir to the Scottish throne), we can draw some conclusions from about his feelings from Malcolm's conversation with Macduff later in the play.  

Malcolm fled to England after Duncan's murder, and when Macduff arrives to speak with him, Malcolm is suspicious of Macduff's motives in attempting to get him to return to Scotland; he fears that Macduff...

Although Malcolm doesn't actually speak when King Duncan, his father, names him the Prince of Cumberland (the heir to the Scottish throne), we can draw some conclusions from about his feelings from Malcolm's conversation with Macduff later in the play.  

Malcolm fled to England after Duncan's murder, and when Macduff arrives to speak with him, Malcolm is suspicious of Macduff's motives in attempting to get him to return to Scotland; he fears that Macduff works for Macbeth and is trying to get him to come home so that Macbeth can kill him.  In order to test Macduff, Malcolm tells him that he has all manner of flaws that ought to prevent Macduff from desiring to see Malcolm installed as king: he claims to be greedy, "deceitful / [...] malicious, smacking of every sin / That has a name" (4.3.71-72).  Because Malcolm insists that his embodiment of these qualities means that he is not going to make a good king, we can understand that he believes that a king's behavior should actually be beyond reproach, that a king really ought to maintain the highest code of honor possible.  Being deceptive or lustful or greedy should disqualify a person from holding this position, from being the leader of a country.

When Macduff declares that not only is Malcolm not fit to rule but he's not fit to live, Malcolm tells him the truth: that this was actually the first time he's ever lied, and he did so to test Macduff.  He says, "What I am truly / Is thine and my poor country's to command [...]" (4.3.150-151).  In other words, he believes that a proper king is at the command of his country, not the reverse.  He wants to serve his countrymen, unlike the treacherous Macbeth, and this is -- for him -- what a good king must do.