There's no dearth of post-apocalyptic games on the market. Metro, based on novels by Dmitry Glukhovsky, is easily up there with the likes of Fallout, even though it has far fewer games. The latest (and likely last) entrant in the series, Metro Exodus, has received a 75% price cut on Steam.
Metro Exodus carries forward the event of 2014's Metro Last Light. Ideally, you should experience Metro Last Light and Metro 2033 to get a full gist of the story. And you can if you have the time because the bundle with all three games has also been heavily discounted by 85%.
In Metro Exodus, you navigate an open-ish world and hop from area to area, trying to get your train through multiple parts of the in-game universe. The game has a hidden morality system that determines what ending you get, and also determines the fate of the numerous companions you cross paths with.
The Gold Edition provides you with access to two pieces of DLC: The Two Colonels and Sam's Story. Both expand upon the stories of two of your companions and add a few hours of gameplay each. While not integral to the plot, they help tie loose ends for those who want closure.
Metro Exodus has relatively light system requirements (Core i7-4470K, GTX 1070/RX Vega 56, 8 GB RAM), but, gamers with higher-end RTX cards can experience it in full ray-traced glory thanks to its Enhanced Edition. This is a separate installation from the regular game because it has beefier textures, and is included in the Steam bundle.