Metal matrix composites enable the combination of the outstanding properties of advanced ceramic and graphitic fibres with the advantages of metallic materials. The efficiency of the reinforcement depends mainly on the characteristics of the fibre/matrix interlayers. Optimized materials can be achieved by an appropriate interface design on the nanoscale. In particular, the bonding and friction conditions for the micromechanical processes and the high temperature behaviour have to be adjusted. This can be accomplished, e.g., by controlling the reactivity between fibres and matrix and by inserting an additional interlayer or layer system which meets specific conditions and can act as diffusion barrier to prevent degrading fibre-matrix reactions and as micromechanically active layer to provide the desired degree of bonding between fibre and matrix.