At the beginning of the scene, Macbeth is brimming with confidence. Several times in the scene he talks about not having anything to fear until Birnam Wood comes to Dunsinane and everybody knows trees can't walk.
He also questions Malcolm's ability. To this seasoned veteran, Malcolm is a boy, not only a boy but one who needed to be rescued at the beginning of the play. Besides, Malcolm was born of women and he could not be killed by any man born of woman.
As for MacDuff, he feels that he has nutralized him when he killed his family because that prediction is not even addressed.
He is overconfident, yet he does express some doubts. He knows that he will not grow old and enjoy all that accompanies old age. He may not die that day, but he know it is only a matter of time before he is killed. He knows that those who live by the sword, die by the sword.
He also wants the doctor to cure Lady Macbeth but the doctor tells him that it is beyond his skill and only she can cure what is wrong with her mind. This is not the answer Macbeth wanted to hear.
By the end of the scene, he is confidently arming for the coming battle.
Macbeth is in quite a worked-up state in this scene. He barges into Dunsinane Hall with his servants and his wife’s doctor and pridefully announces that he is not afraid of the English army OR Malcom. The reason he has no fear, he says, is because of the Witches’ prophecy – “none of woman born” can harm him and he will be secure until “Birnam Wood remove to Dunsinane.” Macbeth has falsely believed that these two events can never happen, but fear is creeping in during this scene and he is starting to break down. He says:
The mind I think with and the courage I have
Shall never sag with doubt or shake with fear.
But little by little, we get the idea that this is false bravado. His servant announces that over 10,000 Englishmen are on their way to the castle, and yet he still contends that he is safe. He tells the soldier that brings him the news:
Go prick your face and hide your fear in a red face,
You lily-livered boy
He is at the height of his prideful ambition in this scene, but the fact that he insists on wearing his armor shows that he is still somewhat fearful of the approaching battle. He says that he will either win and rule forever, or be killed.
Will give me the throne forever or unseat me now.
Either way, it is fine with him. He has lived long enough and life has ceased to give him pleasure. Plus, the doctor tells him that he can do nothing for Lady Macbeth – she must heal herself – and Macbeth will not accept this. He tells the doctor to do something. Give her some herbs or something. So Macbeth, I think, is realizing finally that things are spiraling out of his control.
You can read the enhanced text here at eNotes at the link below (from which my quotes come).