Tantalus committed several offenses that angered the gods, the most common ones being:
* Serving his own son Pelops at a banquet for the gods: This act of cannibalism was a grotesque violation of hospitality and a test of the gods' omniscience. He wanted to see if they could tell the difference between human flesh and animal meat.
* Stealing nectar and ambrosia from the gods' table: Nectar and ambrosia were the food and drink of the gods, granting them immortality. By stealing them, Tantalus was violating their divine privilege and trying to attain immortality for himself or give it to mortals.
* Revealing the secrets of Zeus: It is sometimes mentioned that Tantalus divulged the secrets he learned while dining with the gods, betraying their trust.
Some accounts attribute only one or two of these offenses to Tantalus, while others include all three. The consensus, however, is that Tantalus was arrogant, disrespectful, and attempted to elevate himself to the level of the gods, resulting in his eternal punishment.