Individual atoms or molecules bounce off of their neighbors. A collection of atoms that has no fixed shape, but is able to maintain its volume. This is the source of surface tension. Surface tension is the force that separates a liquid from the air. Bonding is strong and directional.
Subgroups are crystals, glasses, and polymers.
E.g. gemstones, sand, salt. Most natural rocks are formed of interlocking smaller crystals. Your bones are crystalline. You can predict nearest neighbor bonding but not out further. Note that the crystal is very symmetric and its atoms display translational periodicity while the atoms in the glass are arranged in a more random fashion.