Metallic sulfides are compounds formed by the combination of metals with sulfur. They typically have a crystalline structure and can be found in nature as minerals. Common examples include pyrite (iron sulfide) and galena (lead sulfide). These compounds are often important in mining and metallurgy, as they can be sources of valuable metals. In addition to their economic significance, metallic sulfides can also play a role in environmental processes. They can influence the availability of nutrients in soil and water, and some sulfides are used in industrial applications, such as in the production of semiconductors and catalysts.