The thermal paste sits between your CPU’s IHS and the cooler’s heatsink to facilitate thermal conduction. It’s also needed to fill the microscopic gaps between the two seemingly smooth surfaces to ensure maximum contact. While this might sound simple enough, the thermal paste gets more attention than it deserves. People often try to justify the necessity of expensive thermal paste, citing numerous advantages that it holds over the pre-applied paste on your CPU cooler. Aftermarket paste might be technically better than stock thermal paste, but the real-world differences are negligible, at least for most users. That said, those chasing every last ounce of performance from their high-end CPU can and should invest in high-quality thermal paste.