What is a metaphor or simile that is used in act 4 scenes 2 or 3 of macbeth?

Great literature is replete with metaphors and
similes which, by making unsual comparisons between ideas and things, enable readers
understandings of life.

In Scene 2 of Act IV, when the
murderers enter, they are insulted by Macduff's son, and one stabs the boys saying,
"Young fry of treachery," a metaphor for the boy's being the son of a man who is a
traitor.  In the following scene, Macduff's first words contain two similes [comparisons
of unlike things using the words as or
like]:

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Let us rather

Hold
fast the mortal sword, and like good
men

Bestride our down-fall'n
birthdom.

Each new morn New widows howl, new orphans cry,
new sorrows

Strike heaven on the face, that it
resounds

As if it felt with Scotland and yelled
out

Like a syllable of dolor.
(IV,iii,3-9)

Then,
in line 22 of this scene, Malcolm says,

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Though all things foul would wear
the brows of
grace,

Yet grace must still
look so. (IV,iii,22)

This
line means that his thoughts cannot change what a person is; things may look good, but
be filthy; nevertheless, good must still resemble them when they are disguised.  "The
brows of grace" is the appearance of seeming good.

Later in
the scene, Malcolm uses a simile as he says,

black
Macbeth

Will seem as pure as
snow, and the poor state

Esteem him
as a lamb, being compared

With
my confineless harms. (IV,iii, 59-61)

Further in this
scene, Malcom employs a metaphor as he says, "Pour the sweet milk of
concord into hell" as he states that he would cause discord in the world,
destroying peace.