How is Macbeth's opposition presented in Act 3 of Macbeth?

The scene you want to focus on is Act III scene 6, in
which Lennox talks with another Scottish Lord about his suspicions of Macbeth and the
forces that are being raised in opposition to his rule. It is the Lord that tells Lennox
about these forces. He says that Malcolm has gone to England, where he is being helped
by King Edward to raise a force to retake his rightful inheritance that has been so
cruelly snatched away from him by Macbeth. In addition, Macduff has gone there to gain
more support for their cause. Note what he says:

readability="18">

Thither Macduff

Is
gone to pray the holy King, upon his aid

To wake
Northumberland, and warlike Siward;

That, by the help of
these (with him above

To ratify the work), we may
again

Give to our tables meat, sleep to our
nights...

Therefore this
scene is important in giving the audience news of the conflict that is in the offing
between Malcolm and Macduff on the one hand and the forces of Macbeth on the other. This
of course foreshadows Macbeth's eventual defeat and, ironically, the truth of the
prophecies of the witches, for Macbeth will not have an heir that can inherit the crown
from him, and his ambition will end with his death.