Tutorial 3dsMax -- Material Modifier
The Material modifier allows you to animate, or simply change, the assignment of material IDs on an object. If the material ID is animated, the change to a new material ID is abrupt, from one frame to the next.
If you want a gradual blend from one material to another, try animating the Mix parameter on a Blend material.
This modifier does not convert a patch object below it in the modifier stack to a mesh. A patch object input to the Material modifier retains its patch identity
Sometimes completely unknown, the modifiers are very useful during the normal workflow of 3dsMax. These are old videos created with 3dsMax2010 but the modifiers are equal to the latest versions.