In Act 1, Scene 2, Leontes articulates his paranoia about his wife's fidelity through the extended metaphor of the cuckold's horns. In Shakespeare's day, men with adulterous wives were often depicted in art and literature with ram's horns and were subject to mockery for being deceived by their wives. Throughout this scene, Leontes's language describes the metaphorical growth of cuckold's horns on his head as his belief in his wife's infidelity cements itself.
As Leontes watches Hermione give her hand to Polixenes to welcome him to the Sicilian court, he becomes suspicious of their intimacy. As he begins to imagine an affair between them, he calls these images "entertainment / My bosom likes not, nor my brows." While examining his son's face in search of evidence that he was fathered by another man, Leontes is unable to cast aside his suspicions and becomes increasingly agitated, which leads to the imagined "hard'ning of [his] brows" and thus the progression of the growth of his horns. Finally, once Hermione and Polixenes leave together for the garden, Leontes thinks they resemble a married couple and imagines horns affixing themselves to his head: "o'er head and ears a fork'd / one!" This extended metaphor highlights Leontes's fear that his wife's adultery will render him a fool. Of course, the metaphorical growth of Leontes's horns corresponds not to Hermione's actual infidelity, but rather to the amplification of Leontes's delusions. Ironically, it is Leontes's very fear of appearing foolish that turns him into a fool.
As Leontes interrogates his son Mamillius in Act 1, Scene 2, in search of evidence that Hermione has been unfaithful, Leontes's use of similes provides insight into his distrust of women:
Women say so,
That will say anything.
But were they false
As o’erdyed blacks, as wind, as waters, false
As dice are to be wished by one that fixes
No bourn ’twixt his and mine, yet were it true
To say this boy were like me.
Here, Leontes uses similes to suggest that women are artificial like dyed hair, unstable like wind or water, and deceitful like rigged dice. Ironically, his professed view of women is subsequently disproven when he admits that what women have said is true in this case—that is, that his son resembles him. This is an example of situational irony because audiences might expect that, having made this admission about women's truthfulness, Leontes would then rethink his attitude about women overall, and yet he doesn't.
The fact that Leontes can acknowledge this discrepancy between his belief in women's unfaithfulness and the physical evidence that his son is his own, yet remain convinced that Hermione has been unfaithful, shows how intractable his delusion has become: Leontes only sees what he wants to see.