- Terminology: The term "plastics" used to describe a large large segment of polymers has its origins in metallurgy. "Plastic" deformation is a permanent deformation of a material resulting from high stresses, and the "plastics" that are such much a part of the modern world show this behavior quite readily. Similarly, "annealing" was first used in treating metals, but the term has been borrowed by the plastics industry as well.
- Processing: Many of the processes used in these fields are common to each each, and the number is growing more each year. Consider the latest reports about blow molding metals, recalling that injection molding of metals is already old hat.
- Fundamental Science: At a more fundamental level, there is plenty of overlap of the concepts of thermodynamics, rheology, chemical bonding etc.
Just be sure you have a good footing in one of the fields. Generalists never get any of the good stuff.
[*] Not only made by Man, but also by men.