What happens when someone sees the Lord face to face?

It is distinctly mentioned here that the Supreme Personality of Godhead did not appear as an ordinary human being. He appeared before King Nābhi and his associates as the best of all personalities (Puruṣottama). As stated in the Vedas: Nityo nityānāṁ cetanaś cetanānām (Kaṭha Upaniṣad 2.2.13). The Supreme Personality of Godhead is also a living being, but He is the supreme living being. In Bhagavad-gītā (7.7), Lord Kṛṣṇa Himself says, mattaḥ parataraṁ nānyat kiñcid asti dhanañjaya: “O conqueror of wealth [Arjuna], there is no truth superior to Me.” No one is more attractive or more authoritative than Lord Kṛṣṇa. That is one of the differences between God and an ordinary living being. According to this description of the transcendental body of Lord Viṣṇu, the Lord can easily be distinguished from all other living beings. Consequently, Mahārāja Nābhi and his priests and associates all offered the Lord obeisances and began to worship Him with various things.

As stated in Bhagavad-gītā (6.22), yaṁ labdhvā cāparaṁ lābhaṁ manyate nādhikaṁ tataḥ. That is, “Upon gaining this, one thinks that there is no greater gain.” When one realizes God and sees the Lord face to face, one certainly thinks that he has gained the best of all things. Raso ’py asya paraṁ dṛṣṭvā nivartate: when one experiences a higher taste, his consciousness is fixed. After seeing the Supreme Personality of Godhead, one ceases to be attracted by anything material. One then remains steady in his worship of the Supreme Personality of Godhead.

(Source: Srimad Bhagavatam 5.3.3 Purport)