Applying thermal paste is one of the most important steps you’ll take while building a PC. The paste, also known as the thermal compound, is applied to the top of the CPU’s Integrated Heat Spreader (IHS) to fill the air gaps that are formed due to the microscopic imperfections on the surface of the IHS and the metal base of your CPU cooler. This paste essentially paves ways for a more efficient heat transfer to ensure your CPU’s operating temperature remains under the acceptable limits. Simply put, thermal paste helps your CPU stay cool at all times, and you can’t build a PC without it.