Does the coating of M and Ms contain shellac?

Yes, the coating of M&M's does contain shellac, which is a resin obtained from the secretions of the lac bug. Shellac is used to give the candies their shiny appearance and to protect the chocolate inside. However, it's worth noting that some varieties of M&M's may use different coatings or ingredients, so it's always a good idea to check the packaging for specific details.