‘He has a Molson muscle’
My informant, who is from Toronto, Canada, uses the term ‘Molson Muscle’ to describe someone with a beer belly. Molson is one of the most popular Canadian beers drunk in Canada, and so the idea is that in Canada, when someone has a beer belly, it’s the muscle that the man has grown from drinking so much Molson. My informant uses the term mostly around his family and other Canadians, because Molson isn’t a beer that is widely—if at all—distributed in the United States, so the joke would be lost on Americans.
Molson is also one of the cheaper beers you can buy—it is the Canadian Coors—so the folk metaphor is tied not just to Canadians on a whole, but also particularly to the more working class/lower socioeconomic citizens who would drink a lot of Molson, even though the metaphor is used for anyone with a beer belly. I see the folk metaphor as a way to show Canadian pride/nationalism because Molson is the quintessential Canadian beer, while also poking fun at the social class who drinks it most.