The aeroengine is one of the most hostile and demanding environments for any material system. When this is coupled with the ongoing industry requirements for higher thrust levels, lighter weight, and increased efficiency, all at reduced cost, it means that the introduction of advanced composite materials such as metal matrix composites (MMCs) will require intensive and thorough development programmes. Understanding component behaviour from the macro down to the micro material scale will be necessary to ensure that the transition from conventional monolithic metals to metal composites can be made safely. This chapter looks at the potential benefits that aluminium and titanium matrix composites can bring to aeroengines, discusses processing and also considers some of the associated problems.