Mettaton's Dueling With The Stars!
After the human known as Frisk helped the monsters escape the Underground, Mettaton brought his idol skills and MTT Brand to humanity. With numerous successes, it eventually caught the eyes of Industrial Illusions employee; Chumley Huffington. Being a fan of his work, he showed the Glamourous Idol's performances to the head of the business and founder of the entire game; Maxamillian Pegasus.
"Hmm. I do recall hearing about these monsters. I should visit this... Mettaton."
The two met and Mettaton was quite impressed with this one. He did hear about a Children's Card Game and how a lot of it revolved around Monsters. So Pegasus decided to use his influence to assist him with getting to grasps with the game with a one in a lifetime opportunity.
Fast Forward several years, and Mettaton was gifted a package from the Duel Monsters President; his very own custom deck of cards! A deck archetype unique to Mettaton, he aced the entrance exam and was on his way to the prestigious Duel Academy; created by none other than Seto Kaiba.
A member of the Obelisk Blue dormitory, Mettaton would proceed to refine his basic dueling skills and strategy to become the best Idol Duelist, as well as expand the MTT Brand.