Once Matali, the chairoteer of Indra was searching for a bridegroom for his daughter Gunakesi, who was celebrated all over the world for her beauty. Even after searching enough, He couldn't find any suitable husband amongst gods, daityas , gandharvas, men and rishis. He then made a journey to the world of the Nagas.
On his way, he saw the great Rishi Narada. Matali informed Narada, of his mission purpose and then, the well travelled Narada, who knew all the residents of nether world, agreed to join Matali in his quest. After going through various regions in the nether world, Matali foung a Naga youth by the name of Sumukha, whom he found suitable for his daugher. On enquiring with Narada about lineage of Sumukha, he got to know that Sumukha was born in the race of Airavata and his father Chikura was killed by Garuda. When Narada told Sumukha's grand-father Aryaka about Matali's desire to have Sumukha as his son-in-law, he became both happy and sad. He said its an honor to have such an alliance for his grandson and would be more than happy to get Sumukha married to Gunakesi. However, they are scared as when Garuda killed Sumukha's father, he also promised to kill Sumukha within a month.
Matali, who had the lord of the devas as his friend, suggested, they all go to Indra and ask his help in this matter. When they went to meet Indra, they found Lord Vishnu also there, who on hearing their story asked Indra to give Amrutham to Sumukha and make him immortal like other gods. Indra was also scared of Garuda as in the past during a battle with Garuda, he had found his Vajra was also not able to do any damage to Garuda. However after getting assurance from Lord Vishnu, he gave Amrutham to the Naga. Now Sumukha, having drunk Amrutham and having lost fear of Garuda, married Matali's daughter and returned home.
Now, when the mighty Garuda heard what had happened, he got into a rage and was inflamed with anger. He came to Indra and asked him, how dare you gave away my food(the naga Sumukha). Garuda said, although I am of immeasurable strength and also more powerful than you, I still have to be respectful towards you(as Indra is the king of the devas). He further said, that through my strength I can carry the weight of three worlds without getting fatigue, yet due to the respect I give you, I carry your younger brother(Vishnu) on my back and I also protect his flag. There is no one in the whole universe who is capable of bearing such heavy burden.
Lord Vishnu who was also listening to these proud words of Garuda, said smilingly to Garuda. "You are very weak and yet you are saying all these proud words". All the three worlds united can't bear my weight, it is me only who bears my weight. If you are capable to bear the weight of my right arm only, then i can assume your words are true. Saying this, Lord Vishnu gently put his right arm on Garuda's shoulders. Just by the touch of that arm, Garuda fell down, became breathless and lost his senses. He thought that one arm was itself like weight of complete earth along with its mountains. Garuda was gasping of life and started losing all his feathers. Immediately, he bowed down to the great Lord and asked for forgiveness. He said, this strength of yours was never known to me and this strength of yours used to make me unequalled. Please forgive this winged created. Lord Vishnu became happy, told Garuda never to boast about his strength in future and also asked him to keep the naga Sumukha on his breast.
This story was told by the Kanwa Rishi to Duryodhana and others in the Kuru assembly to let them know that Krishna is no one else but that Lord Vishnu and Kauravas don't stand a chance against Pandavas who are ever protected by Krishna.
