In a large mixing bowl, combine the oats, Nutella, honey, vanilla extract, and a pinch of salt if desired. Stir until well combined and the mixture holds together.
Gently fold in the M&M candies until evenly distributed throughout the mixture.
Using your hands, scoop out small portions of the mixture and roll them into balls. If the mixture is too sticky, you can wet your hands with water or lightly coat them with oil to prevent sticking.
If desired, press additional M&M candies into the surface of the balls for decoration.
Place the balls on a baking sheet lined with parchment paper and refrigerate for at least 30 minutes to firm up.
