Good Brabantio. Take up this mangled matter at the best. 
Men do their broken weapons rather use 
Than their bare hands.  (1.3.173–176) 

After hearing Othello’s convincing account of how he won Desdemona’s love without witchcraft, the Duke uses this metaphor to tell Brabanzio that his case against Othello has just been dealt a major blow; if Brabanzio has any hope of winning, he will have to fight back with the weapons that Othello has just broken.  

Virtue? A fig! 'Tis in ourselves that we are thus or thus. Our bodies are our gardens, to the which our wills are gardeners. So that if we will plant nettles or sow lettuce, set hyssop and weed up thyme, supply it with one gender of herbs or distract it with many—either to have it sterile with idleness, or manured with industry—why, the power and corrigible authority of this lies in our wills. (1.3.307) 

When Roderigo suggests that suicide might be the best remedy for his unrequited love for Desdemona, Iago encourages him to take control of the situation by comparing our bodies to gardens and our freewill to gardeners who have the power to choose whether to plant weeds or the crops of our choice.  

The food that to him now is as luscious as locusts shall be to him shortly as bitter as coloquintida. (1.3.309) 

Here Iago refers to Desdemona as “food” for Othello, assuring Roderigo that while Othello may find Desdemona as delicious as locusts (a delicacy) now, soon enough she will taste like coloquintida (a bitter plant used as a laxative). 

There are many events in the womb of time which will be delivered. (1.3) 

In this metaphor, Iago assures Roderigo that his future is promising by comparing the events of the future to children yet to be born. 

For that I do suspect the lusty Moor 
Hath leaped into my seat. The thought whereof 
Doth, like a poisonous mineral, gnaw my inwards. (2.1.220–222) 

In these lines, Iago uses a euphemism (“leaped into my seat”) to express his suspicion that Othello has slept with his wife, Emilia; he then compares his suspicion to a poison that is eating away at him from the inside.

You are but now cast in his mood, a punishment more in policy than in malice, even so as one would beat his offenseless dog to affright an imperious lion. (2.3.227) 

Here Iago reassures the despondent Cassio, who has just been relieved of his command, that Othello isn’t really angry with him, but is only making a temporary example of him, like a person who beats his innocent dog as a show of force to scare away a lion. 

Good name in man and woman, dear my lord, 
Is the immediate jewel of their souls. 
Who steals my purse steals trash. 'Tis something, nothing: 
'Twas mine, ’tis his, and has been slave to thousands. 
But he that filches from me my good name 
Robs me of that which not enriches him 
And makes me poor indeed. (3.3.160–166) 

In this extended metaphor, Iago compares a good reputation to a precious jewel that, unlike money, has true and lasting value for its owner, yet is worthless to anyone who would try to steal it.  

Oh, beware, my lord, of jealousy! 
It is the green-eyed monster which doth mock 
The meat it feeds on. (3.3.170–172) 

In this famous metaphor, Iago cautions Othello by comparing jealousy to a green-eyed monster that ridicules its victims even as it is eating them; ironically, the monstrous Iago is at this very moment seeding jealousy in Othello.  

I hope my noble lord esteems me honest. 

Oh, ay, as summer flies are in the shambles, 
That quicken even with blowing. (4.2.68–69) 

Here Othello sarcastically tells Desdemona he thinks she is as honest, or faithful, as flies in a slaughterhouse: simply blow on them and they fly away

Yet I’ll not shed her blood, 
Nor scar that whiter skin of hers than snow 
And smooth as monumental alabaster. (5.2.3–5) 

In these lines from the play’s final scene, Othello compares the whiteness of Desdemona’s skin to snow and alabaster (a white mineral), momentarily questioning his plan to kill her and thus stain her whiteness with blood.