I'm not much of a drinker, and I didn't know what a Moscow Mule was until I saw the Bali Hai episode of Better Call Saul. The drink, made from vodka, ginger beer, and lime juice, poured over ice, was served to Kim Wexler (my favorite character on the show, played by Rhea Seehorn) in a copper mug. Recently, I went on vacation with my wife, and she ordered a Moscow Mule at a restaurant. It was served in a copper mug. It turns out you are supposed to serve them that way.
The origins of the Moscow Mule are a bit murky, but it appears to have been invented in the early 1940s by the owner of a Hollywood pub on the Sunset Strip called the Cock 'n' Bull. The bartender wanted to clean out a slow-moving stockpile of Smirnoff's and bottled ginger beer that had been gathering dust on the shelves in the backroom, so he mixed them together and started serving them in copper mugs to the movie stars who frequented the pub. It became an instant hit, at least until McCarthyism scared people away from anything with the taint of Sovietism to it. But the Moscow Mule had a kick that people liked, and it made a comeback in the 1960s, which it enjoys today.
You can buy a set of 4 copper mugs with brass handles for $(removed) on Amazon. I just bought a set, and am looking forward to mixing up a batch of Moscow Mules the next time we have friends over for dinner.