Please explain Lady Macbeth's speeches in Act 1 Scene 5 of Macbeth.

Lady Macbeth is one of Shakespeare's strongest women and
is often considered a villain of the play.  In an odd way, that's high praise, as this
important function was usually reserved for a male character in the
play.

We first meet her in Act I, scene V.  She is reading
a letter from Macbeth, in which he describes his prophetic meeting with the witches. 
"Hail, king thou shalt be!" is all the motivation that Lady M needs to decide that her
husband should become king sooner rather than later:

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Glamis thou art, and Cawdor, and shalt
be

What thou art promised:  yet I do fear thy
nature;

It is too full o' the milk of human
kindness...

And, in
recognizing her husband's weakness, a kind heart, Lady M. sets herself up as the driving
force behind a plot to kill the present king, Duncan, while he sleeps in their home that
night.

In her famous lines (39-55), she invokes whatever
magic it might take to give her the strength and courage of a man (implying that her
husband lacks this) to get the job done -- which is
murder.

Come,
thick night,

And pall thee in the dunnest smoke of
hell,

That my keen knife see not the wound it
makes,

Nor heaven peep through the blanket of the
dark,

To cry, 'Hold,
hold!

She sets herself up as
a villain here, invoking the forces of Hell and cautioning those of Heaven to stay out
of her scheme.

Macbeth arrives and she not only greets him
by the titles he owns (Glamis and Cawdor), but also calls him "Greater than both
hereafter."  She wastes no time in telling Macbeth that Duncan will never leave their
home alive ("O, never/Shall sun that morrow see!").  While Macbeth isn't convinced of
her hastily described plan, Lady M, is clearly in charge -- "Leave all the rest to
me."