There certainly is something historically appealing about hoisting an overflowing chalice of one’s own homemade vinous deliciousness. In ancient times metal was a common material from which to fashion drinking cups. From medieval castles to Viking mead-halls, brass, pewter, and silver goblets have been part of our world’s imbibing culture. However, such romantic imaginings are best left to be just that as drinking wine out of a metal vessel, especially brass, will most likely change your wine and likely for the worse.
In my personal experience, any time I’ve had wine out of a metal cup it has made the wine taste metallic. When I was a college student I used to participate in Renaissance fairs and historical re-enactment events where we drank everything from water to beer to wine from clay, wood, and yes, metal vessels. In those historical epochs, after all, glass or crystal was a luxury only the very wealthy could afford. And afford it they did, for good reason. Drinking just about anything out of metal (except perhaps stainless steel) will likely make it taste metallic.
Don’t just take my anecdotal experience into account. Chemistry tells us that brass is an alloy of copper and zinc. Wine is also an excellent solvent, being a mixture of mostly water, alcohol, and acid in addition to smaller percentages of things like aroma and phenolic compounds. All three of those first components, upon coming in contact with the brass, will start to react with the metal itself. After all, copper is often used to treat wines that have a sulfide defect and before we could add copper sulfate in liquid form, winemakers in France would pass the wine through brass pipes to create the same effect.
So if your wine is suffering from a sulfide defect (smells like rotten eggs) it’s possible that drinking from a brass cup could make the wine smell better. If your wine is normal, the copper in the brass will not help your wine and might negatively affect quality because you might be extracting unnecessary metals and ions into your wine. When winemakers use copper to treat wine with sulfide issues they always use the minimum amount needed because 1) excess copper is toxic and 2) it can wreck the mouthfeel and shut down good aromatic elements.
Long story short? Metal cups can be fun, especially if you’re dressing up as a Game of Thrones character for Halloween. For quality drinking and proper wine tasting, however, a neutral vessel of glass or crystal is almost always best.