How did Socrates compare himself to a gadfly stirring a sluggish horse?

In his defense at his trial, as recorded in Plato's Apology, Socrates famously compared himself to a gadfly assigned by the divine to stir a large, sluggish horse—which represented the city of Athens.123

Socrates used this metaphor to explain his philosophical mission: just as a gadfly’s bite is painful but necessary to rouse a lethargic animal, his persistent questioning and cross-examination were intended to stimulate serious moral reflection among his fellow citizens. He argued that he was performing a great service to the city by puncturing the complacent, unexamined beliefs of those who falsely claimed to possess wisdom.23

Ultimately, Socrates recognized that this role was inherently provocative. He noted that the horse naturally resents the fly's sting, just as many Athenians resented being made to look foolish or being forced to confront their own lack of understanding. This resistance to self-examination, he believed, was a fundamental psychological force that led to the hostility he faced and his eventual conviction.2