While it is true that atoms are mostly empty space, the reason why matter seems solid is due to the strong electromagnetic force between the positively charged nuclei and the negatively charged electrons in the atom. This force causes the electrons to orbit the nucleus in specific patterns, creating a stable atomic structure.

At the macroscopic level, when atoms come together to form molecules and materials, the electromagnetic forces between the electrons and nuclei of different atoms interact, giving rise to various interatomic bonds such as covalent bonds, ionic bonds, and metallic bonds. These bonds hold the atoms and molecules together, forming solids, liquids, and gases.

In Solids, these interatomic forces are very strong, resulting in a rigid structure where the atoms or molecules are tightly packed and fixed in their positions. This strong binding prevents the atoms and molecules from moving freely, giving solids their characteristic rigidity and firmness.