Shakespeare heavily uses the supernatural in the opening of this scene to give a feeling of fear and malevolence. The witches casting a spell shows that they have power here. The witches are also using the natural world for the unnatural means
The second apparition appears- a bloody child
Double double toil and trouble, fire burn and cauldron bubble
Macbeth's encounter with the witches shows how his character has changed. In act 1 he was cautious of the witches and sceptical of their power, however now he goes to them to gain knowledge. He is arrogant and demanding of the witches even though they have more power than him. He is over confident and has misguided feelings about power.
Even till destruction sicken, answer meTo what I ask you.
I conjure you by that which you profess— Howe'er you come to know it—answer me.
Despite Macbeth's confidence the witches answer him and give him his wish. They conjure up apparitions that give Macbeth advice. The first is a head. Macbeth's arrogance is further shown as he tries to command the spirit. he thinks he is above even the supernatural
But one word more—
Macbeth! Macbeth! Macbeth! Beware Macduff. Beware the thane of Fife. Let me go. Enough.
He will not be commanded.
Then live Macduff: what need i fear of thee?
Be bloody, bold, and resolute. Laugh to scornThe power of man, for none of woman bornShall harm Macbeth.
The final apparition is a a crowned child, however after this, the ghost of Banquo returns accompanied by eight kings, all of whom are his decedents. This shocks Macbeth and he becomes bent on keeping his power.
Horrible sight! Now I see ’tis true;For the blood-boltered Banquo smiles upon meAnd points at them for his.
The very firstlings of my heart shall beThe firstlings of my hand. And even now,To crown my thoughts with acts, be it thought and done
After the witches vanish, Lennox brings news that Macduff has fled to England. This angers Macbeth as his plans have been thwarted by time. From now on whenever he things of an idea he will carry it out immediately. This shows his determined nature to keep his power and he will not hold back anymore.