How does Shakespeare use language to make Macbeth sound confident?

In Act 4, scene 1, Shakespeare presents a very confident Macbeth, in part, through his use of imperative (command) statements.  He does not ask questions or seek assurance as he did when he spoke with the witches for the first time.  No, now he demands answers, saying, "I conjure you by that which you profess / (Howe'er you come to know it), answer me [....] answer me / To what I ask you" (4.1.51-64).  The Weird Sisters respond differently to him now, allowing him to "Demand" things of them (4.1.66).  When they offer to call their "masters" for Macbeth so that he may speak to them directly, Macbeth, rather nonchalantly, says, "Call 'em.  Let me see 'em," as though he is completely unconcerned that he could be speaking with demons or devils (4.1.70).  Even when he's presented with the witches' "masters," he still attempts to make demands of them though the sisters tell him that these "will not be commanded" (4.1.86).  He is even somewhat irreverent and jokey when presented with the second apparition who calls his name three times, when he responds, "Had I three ears, I'd hear thee" (4.1.89).  Perhaps he's trying to exercise his wit in order to cover up some nervousness, but it makes him seem even more arrogant than his demands do.  

Finally, when he asks about Banquo's descendants and whether or not they will ever reign, the sisters tell him that he shouldn't try to learn any more, but he persists, "Deny me this, / And an eternal curse fall on you!" (4.1.119-120).  His confidence (and arrogance) reaches epic proportions here; he is no longer in awe or fearful of the sisters, and he's gone beyond making jokes and demands.  Now he actually threatens to curse them if they disobey them.