Why did Hades choose Cerberus to be the guard of the Underworld?

Hades chose Cerberus, the three-headed dog, as the guardian of the Underworld to ensure that the souls of the dead could not escape and that the living would not intrude. Cerberus symbolizes loyalty and ferocity, making him an effective deterrent against any attempts to breach the realm of the dead. Additionally, the three heads represent the past, present, and future, underscoring Cerberus's role in overseeing the souls' journey. Thus, Cerberus embodies both protection and the inevitability of death, aligning perfectly with Hades's dominion.