Primer is an essential foundation that ensures paint adheres correctly to the surface. It seals porous materials like new drywall or raw wood, preventing the finish coat from soaking in unevenly. Primer also provides a uniform surface that helps the final color appear more vibrant. Furthermore, specialized primers can block stains, prevent tannin bleed, and inhibit mold growth, making them indispensable for ensuring a long-lasting and professional-looking application.