Malcolm and Macduff’s relationship is important because they are loyal to Scotland and encourage one another to do what is needed to remove Macbeth from the throne. As future king and the leader of the army against Macbeth, Malcolm needs a loyal supporter like Macduff.
King Duncan had two sons, Malcolm and Donalbain. Although Malcolm was young, he was the older son and therefore named Duncan’s successor and Donalbain does not seem to have been verycommitted. Macduff encouraged Malcolm to be king, and Malcolm tempted Macduff to see if he was loyal. At the same time, Malcolm encourages Macduff to turn his grief for his murdered family into vengeful hate.
Bleed, bleed, poor country!
Great tyranny, lay thou thy basis sure,
For goodness dare not check thee. (Act 5, scene 3, enotes etext p. 68)
When Macduff tells Malcolm that he is not “treacherous” and Malcolm replies “But Macbeth is” he is reminding Macduff that they have a responsibility to the kingdom and to avenge his family (p. 67). Malcolm tempts Macbeth by giving him reasons why he is too inexperienced to be king and he’ll be easily corrupted, but Macduff is not tempted. He encourages Malcolm, leading him to believe he can fully trust Macbeth.
The relationship between Malcolm and Macduff is important for several reasons: Malcolm is the righful heir to the throne of Scotland, and Macduff is one of the few Scottish Thanes to pledge a clear alliance to King Duncan and his sons.
After the murder of his father by Macbeth and Lady MAcbeth, Malcolm would havebeen named the next King of Scotland, had he not fled to England. He left because he felt that he could not trust any of the thanes and he was unsure of who could have committed the murder. Macduff quickly lost "trust" in MAcbeth when Macbeth made the mistake of admitting to the murder of the Duncan's guards, which immediately implicated Macbeth in Duncan's.
Macduff made the decision, to the detriment of his entire family to not go to Macbeths coronation and headed to England, where Maclcolm had fled to form and alliance with him to oust Macbeth and allow Malcolm to take his place as the rightful King of Scotland.