The paper presents a discussion of the various types of ceramic joining within a conceptual framework based on the fundamentals of wetting, adhesion, and the thermodynamics of interfacial reactions. Examples are given of solid state diffusion bonding of Pt to alumina and brazing of AlN. Most ceramic-metal bonding is conducted at high temperatures, where chemical reaction is to be expected. The way in which bond strength is affected by chemical reaction at ceramic-metal interfaces is also discussed.