Why does shakespeare open the play with the witches first?

Shakespeare opens with the witches in order to foreshadow what occurs later in the play.

Explanation:

Though you don't learn much, the opening witch scene helps to predict the eventual outcome of the play, a tactic frequently used by Shakespeare. Shakespeare uses foreshadowing very often in his plays.

once upon a midnight dreary, while i pondered, weak and weary,

explanation:

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