Users who already own Metro Exodus will receive the Enhanced Edition as a free upgrade.
As previously announced, here are all the upgrades coming to Metro Exodus Enhanced Edition for PC:
Full ray traced lighting throughout—every light source is now ray traced. Next-gen ray tracing and denoising. Next-gen temporal reconstruction technology. Per-pixel ray traced global illumination. Ray traced emissive surfaces with area shadows. Infinite number of ray traced light bounces.