One of the most important functions of yellow primer is improving paint adhesion. Many surfaces, such as metal, wood, plastic, and previously painted materials, can be difficult for ordinary paint to bond with directly. Primer forms an intermediate layer between the surface and the topcoat. This helps prevent peeling, cracking, and uneven coverage. By preparing the surface properly, yellow primer can significantly improve the durability and appearance of the finished paintwork. Yellow primer is particularly useful on metal surfaces. Bare metal can be vulnerable to moisture, oxidation, and corrosion. A suitable primer provides a protective barrier that reduces direct exposure to environmental conditions.