What is a summary of Portia's speech?

Portia's eloquent speech in Merchant of Venice is often regarded as one of Shakespeare's finest and most poetic monologues (alongside, of course, with Hamlet, Richard III, and Cleopatra). In it, Portia, disguised as a young male lawyer named Balthazaar, pleads with Shylock, a wealthy moneylender and the play's main antagonist, to have mercy upon Antonio.
As usual with Shakespearean monologues, the language is rich, poetic, and often complex. Taking the speech in several pieces will help analyze the entire piece.
When Shylock ponders why he must give mercy, Portia begins the monologue:

The quality of mercy is not strained
It droppeth as the gentle rain from heaven
Upon the place beneath. It is twice blest
It blesseth him that gives and him that takes

Here, Portia suggests mercy to not be necessary, for it is only the kindhearted that are able to give it. She suggests that it benefits those who give mercy and those who receive it. In other words, to give mercy is to be, in a sense, Saintlike. (Pay attention to the second line, "...the gentle rain from heaven". She then continues, telling Shylock that mercy benefits kings, queens, and monarchs even more than their own crown. Merciful kings are respected and powerful kings, she suggests, and she goes on to connect mercy to religion once again:

But mercy is above this sceptred sway;
It is enthroned in the hearts of kings,
It is an attribute to God himself

God is merciful, and if God is the most powerful being of all, even tyrants should aim to share characteristics with Him. She tells Shylock that mercy is divine, powerful, and wholly respectable. The speech continues:

Though justice be they plea, consider this
That, in the course of justice, none of us
Should see salvation: we do pray for mercy;

Here, she is suggesting that if any human asks for proper justice, especially to God, there is nothing but damnation in their future, for all humans are sinners and inherently immoral. Consequently, Portia suggests, one can only ask for mercy when it becomes time for judgment.
As a whole, Portia's speech is a plea with Shylock to have mercy upon Antonio, for mercy is a divine and God-like attribute. Mercy gives power and morality to those who offer it, and it obviously benefits those who receive it.
There is a sense of irony, however, when only a few lines later Portia agrees with a crowd of angry spectators who mercilessly demand that Shylock forfeit half his wealth and convert to another religion, thus losing his own identity.
https://poets.org/poem/merchant-venice-act-iv-scene-i-quality-mercy-not-strained