Any metallic structure consists of an array of positively charged ions in a sea of electrons. Actual metal structures are not perfect lattices but contain imperfections or dislocations. The dislocations enable the metal to be deformed. Alloys are formed by replacing some of the ions in the parent lattice by ions of the alloying metal to form a solid solution. The degree of solid solution depends on the geometry of the system: the relative sizes of the two ions. Some metals also form compounds and the likelihood of this occurring depends on the relative electronegativity values of the elements concerned. It is shown that the ionic sizes and electronegativity values can be used together to form a solubility chart and such a chart is constructed for lead and its potential alloys. From the chart, it is possible to explain the properties of lead alloys, such as hardness, creep strength, grain-refining activity and castability. The grain boundaries in alloy structures are full of dislocations and are therefore areas of high activity. It is shown that, in some cases, severe intergranular corrosion can occur which could result in disintegration of a battery grid and premature failure of a battery. The above principles of metal and alloy structures are illustrated by examples of actual battery grid alloys and their properties. Possible future developments of alloys are also proposed.