how does shakespeare use dramatic irony as a tool/ catalyst in macbeth?

In plays, dramatic irony exists when we as the audience
know background details that the characters on the stage do not. In Macbeth, we know
that Macbeth has been named Thane of Cawdor before he does.  When the three witches make
their predictions, he believes they are looking into his future, so when Ross brings him
the news he trusts the witches predictions while we know the scene has already been set.
Dramatic irony occurs again when King Duncan visits Macbeth's castle.  The audience
knows that Lady Macbeth has convinced Macbeth to kill Duncan in order to gain the crown,
but as the king and his attendants arrive, Duncan comments on the nice weather and how
it is a sign of good things to come.  When in actuality we know his death is. In act IV
Ross meets Malcolm and MacDuff in England.  When they meet MacDuff asks about his
family, and Ross says they are okay by saying that they are “at peace”, but the audience
knows this is not true because Macbeth has had his wife and son murdered in the previous
scene.