This invention pertains to highly filled polymer compositions comprising a low molecular weight ethylene and/or alpha olefin homopolymers and copolymers, or blends therefrom, filled with high concentrations of fillers or additives. Examples of such fillers or additives include fire retardants, talc, ceramic manufacturing agents, color concentrates, crosslinking agents, and blowing agents. Because of the low crystallinity (and therefore high percentage of amorphous phase) and low viscosities of the base polymers, highly processable compositions can be formed containing even if containing relatively high loadings of fillers or additives. Such highly filled compositions are thus ideally suited as concentrates or masterbatch formulations for a variety of different compounding applications.