Milan's bar culture runs on two rhythms: the morning espresso standing at a zinc bar, and the evening aperitivo. The aperitivo — a drink, usually a Campari Spritz or Negroni, accompanied by free snacks — is a Milanese institution, and between 18:00 and 21:00 most bars put out a generous spread that functions as a light dinner.
The Navigli canal district and the Brera neighbourhood are the most atmospheric areas for bar-hopping. The centre around the Duomo has more tourist-facing places, though Camparino in Galleria and Bar Basso are genuine institutions worth seeking out wherever you are staying.