The Rusty Nail is traditionally made with Scotch whisky, Drambuie, and ice.
Drambuie is a Scotch-based liqueur flavored with honey, herbs, and spices. Combining it with Scotch creates a spirit-forward drink that is sweeter and more aromatic than neat whisky. The cocktail is commonly served over ice in an old-fashioned glass, although proportions differ between recipes.
The drink became especially prominent in the United States during the mid-20th century and was associated with the Rat Pack and the 1960s. Its exact origin is uncertain, and several earlier whisky-and-liqueur combinations have been proposed as possible predecessors.
A Rusty Nail is not the same as a Rob Roy, which combines Scotch with sweet vermouth. It also differs from a Godfather, which pairs Scotch with amaretto. Drambuie is the ingredient that gives the Rusty Nail its defining honeyed, herbal character.