What are some motifs that help convey external conflict in Macbeth?

In Shakespeare's Macbeth, there are
several motifs, or recurring structures, literary devices, and contrasts, that serve in
the development of conflict.  Here are some that contribute more to internal
conflicts and external
ones:

Manhood

Throughout
the play, the question of what it means to be a man is repeatedly raised.  With the
captain's description of the "brave Macbeth" in Act I, manhood seems rather brutal as he
"unseamed" his enemy.  Then in Scene 7, Lady Macbeth questions his manhood and Macbeth
replies that he has done all that he can. In Act II when Macbeth has twinges of
conscience about killing King Duncan, Lady Macbeth again challenges his manhood.  Later
in this act in his regret, Macbeth wonders what type of man he is. Towards the end of
the play, Macbeth tells his wife,

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Unsafe the while, that we
Must lave
our honors in these flattering streams,
And make our faces vizards to our
hearts,
Disguising what they are.
(3.2.35-38) 

In addition to
Macbeth's conflict with what it is to be a man, Malcolm ponders the question in Act II,
as well as he says,

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To show an unfelt sorrow is an
office

Which the false man does easy.  I'll to England
(2.3.157-158)

Violence

Although
most of the murder take place off stage, Macbeth is a very violent
play with graphic descriptions of the carnage
throughout. 

Phantasmorgia

Hallucinations
and visions are prevalent from beginning to end.  Macbeth imagines the daggers, the
ghost of Banquo, the moving of the forest, Birnam Wood.  Lady Macbeth, of course,
sleepwalks and imagines that her hands and the steps are covered in
blood.

Nature and the
unnatural

The conflicts in the play result
from the unnaturalness of Macbeth, who kills his king, friends, and a woman and child. 
Ironically, it is the unnaturalness of the moving Birnam Wood which kills
Macbeth.

Heaven and
Hell

Macbeth speaks often of heaven and
hell; in his soliloquies he often mentions "the life to come"; he tells Duncan that the
bell is a knell beckoning him to heaven or to hell; he often ponders that he will end in
hell.