Metal matrix composites with high volume fraction of reinforcement are attractive in view of the possibility to further enhance TC by the use of high TC components and the flexibility to adjust the CTE by controlling the content of reinforcement. Al and Cu were usually used as metal matrix due to their high TCs, and the reinforcements involved SiC, carbon and diamond. On the consideration that the composites produced from the same reinforcement have similar difficulties during fabrication, the composites with high TC were divided into three main categories: SiC/metal, C/metal and diamond/metal composites. Owing to the fact that specific thermal conductivity (thermal conductivity divided by density) of Al-based composites was higher than that of Cu-based composites, Al-based composites are more desirable in avionic applications where light weight is demanded.