Various people help Macbeth at various times of the play. Banquo helps him in the battle which has just ended when the play begins. He gets murderers to help him, and the witches, and his servant Seyton.
Does he have a plan? No, unfortunately. He is persuaded against his better judgement to go along with his wife's murder plan, but from that point forth, he reacts with increasing irrationality to what is going on around him, often by killing someone in the hope that it will improve matters, which it never does. But once he agrees to act against his reason in killing Duncan, there is no more planning for him.
He says this is his way of seeing whether Macduff is a spy for Macbeth. Anyone genuinely wanting to help Malcolm to overthrow Macbeth because he believes Malcolm is better would refuse to follow Malcolm if he was actually worse than Macbeth.
Malcolm promised Macduff that he would send an army to help him overthrow Macbeth.
Lennox informs Macbeth that Macduff has fled to England to seek help from King Edward to overthrow him.
Macduff is trying to defeat Macbeth and overthrow him as king of Scotland. He is motivated by his desire to avenge the murder of his family, which was ordered by Macbeth. Macduff's ultimate goal is to restore peace and order to Scotland by removing Macbeth from power.
Macduff is in England during Act 3. He has gone there to seek help from King Edward of England to overthrow Macbeth and restore rightful rule to Scotland.
Macduff seeks help from Malcolm, Duncan's son and rightful heir to the throne of Scotland. They form an alliance to overthrow Macbeth and restore order to the kingdom.
The English king, Edward the Confessor, has offered to provide troops and support to help defeat Macbeth and restore Malcolm to the throne of Scotland. This assistance comes after Malcolm sought refuge in England following the murder of his father, King Duncan, by Macbeth.
Macbeth didn't think Macduff was a threat because the witches said "None of woman born shall harm Macbeth." Macbeth welcomes this good news and, assuming Macduff was born the natural way, Macbeth thinks he has nothing to fear.
Malcolm fled to England after his father, King Duncan, was murdered. He went to seek help and support from King Edward to overthrow Macbeth and restore order in Scotland.
Banquo, Fleance, Lady Macduff and her children
Malcolm, son of King Duncan, was crowned King of Scotland after Macbeth's death. He was able to reclaim the throne with the help of his ally, Macduff.
In Act IV of "Macbeth," hints of the gathering forces of opposition to Macbeth include Macduff's departure to seek help from Malcolm and other nobles to overthrow Macbeth, as well as the gathering of an army to challenge Macbeth's rule. Additionally, the witches' prophecies to Macbeth provide him with a false sense of security, leading him to underestimate the threat posed by the growing opposition against him.