While there are many iterations of mulled wine, most traditional variants typically include red wine; a sweetening agent like honey, maple syrup or sugar; spices that can range the gamut from cloves, cinnamon and star anise; aromatics like ginger and often another alcoholic agent like brandy or rum. The fruity finish is often furnished courtesy of lemons or oranges, which add lovely nuanced citrus notes to the drink.
This entire assemblage is then heated together, sending out spice-riddled perfumed notes and imbuing the drink with lovely spice and fruit accents.