A primer is a preparatory coating applied to surfaces before painting. It helps improve adhesion, ensuring that the topcoat adheres better and lasts longer. Primers can be used on various materials, including wood, metal, and drywall, and they often seal the surface to prevent stains from bleeding through. Primers come in different formulations, such as oil-based and water-based, each suited for specific applications. Using a primer can enhance the final appearance of the paint job by providing a uniform base. This step is essential for achieving a professional finish and prolonging the life of the paint, making it a crucial part of the painting process.