Being "filled" means being endowed with a spiritual quality. When the material in question is good -- water, food, people who represent good things, etc. -- it means getting a desire for good and an understanding of truth from the Lord. When the material is bad -- dust, flies, emotions like despair or terror, etc. -- it means being overwhelmed and enslaved by the desire for evil and the false, twisted logic that supports it. There are a number of references in the Bible to "filling the hand," which has a specific meaning and is dealt with separately.