What is the relationship between Malcolm and Scotland?
Malcolm is the oldest son of Duncan, the current king of Scotland. Therefore, Malcolm is a prince of Scotland. Further, Duncan names Malcolm the Prince of Cumberland in Act 1, Scene 4, and this is the title for the heir to the Scottish throne. In other words, Malcolm is in line to be the next king of Scotland.
Malcolm seems to genuinely care about his country. He flees to England after his father's murder to protect himself, but he also wants King Edward, of England, to help him to raise an army with which he can return to Scotland and overthrow the tyrant, Macbeth. When Macduff first speaks with Malcolm, Malcolm suspects him of working for Macbeth and tests him by claiming that he has every terrible quality and would therefore make an awful king. Once Macduff proves his own loyalty to Scotland by proclaiming that not only is he not fit to reign, he is not fit to live, Malcolm knows that he is honest. Malcolm says that he is his "poor country's to command," and this helps us to understand that he will be a very good king with his country's interests, and not his own, closest to his heart (4.3.151).