Materials science includes those parts of chemistry, physics, geology, and even biology that deal with the physical, chemical or biological properties of materials. It is usually considered an applied science, in which the properties under study have some industrial purpose.
Materials science encompasses all four classes of materials, the study of each of which may be considered a separate field: metals (1) and metallurgy, ceramics(2), semiconductors and other electronic materials, polymers(3), composites (4), and Biomaterials which may consist of the materials classes 1-4. Metallurgy and ceramics have long and separate histories as engineering disciplines, but because the science that underlies these disciplines applies to all classes of materials, materials science is recognized as a distinct discipline.
Continuum mechanics --- the study of solids and fluids, assuming that they are continuous materials (rather than made of atoms).
Note that some practitioners often consider rheology a sub-field of materials science, because it can cover any material that flows. However, a typical rheology paper covers non-Newtonian fluid dynamics, so we place it as a sub-field of Continuum mechanics. See also granular material.
