The game involves infantry, tanks, and much larger machines (Titans) fighting battles on a tabletop with models of hills, forests, buildings, etc. Each player picks the units of their army and controls that army during the battle. The setting in which these battles take place is a not-very-realistic far-future science fiction universe, and the armies vary in technology levels and specialities. Yes, it is playing with toys, but the wargame aspect is a lot of fun.

Command Infantry : A Space Marine Commander and a Psychic, plus some marines

Infantry : Devastators, Assault Marines, and Terminators

Infantry and terrain : Individually mounted Space Marines among alien plantlife.

Infantry and terrain : More individually mounted Space Marines among alien plantlife.

Land Raider

Space Marine Tanks : Whirlwind, Vindicator, Razorback

More Space Marine Tanks : Leman Russ (actually Imperial Guard tank), and two styles of Predator.

A comparison of the 2nd version Thunderhawk and the current 3rd. I don't have any of the first version, though it has an outline on the cards from Space Marine.
A picture of both kinds. The big one is not completely assembled.
A color picture from 1996 Epic catalog.
A picture from earlier catalog.

Not related to Space Marines, but from the 1996 catalog:
A picture of what was in the pipeline at the time.
And another.