The document summarizes key concepts about materials including: 1) At the atomic level, materials are composed of elements with distinct atomic structures, which bond together in crystalline or noncrystalline forms. Common bonding types include ionic, covalent, and metallic. 2) Crystalline materials have long-range ordered atomic structures with repeating unit cells, while noncrystalline materials lack long-range order. 3) Metals typically have body-centered cubic, face-centered cubic, or hexagonal crystalline structures and metallic bonding, making them strong yet ductile. Ceramics and polymers have other bonding types and properties.