In general, you animate a material by changing its factors in different keyframes while the Animate button is turned on. The values are interpolated between keyframes, just as when you animate transforms and modifiers. These are the factors you can animate:
A component's color
A bitmap's Amount value
The material's highlight control values
Be aware that the tracks for a material applied to an object are distinct from the material tracks that belong to the Material Editor: animating a material in the Material Editor affects the scene only if the material is hot.