Metro 2033 is free to own forever via Steam. As long as you claim a copy before 15th March at about 5pm UTC.
Note that this game and the other titles in the franchise have been free before via Epic Games. So you may already have the games on Epic if you follow this forum section.
Metro 2033 Game Description:
Set in the shattered subway of a post apocalyptic Moscow, Metro 2033 is a story of intensive underground survival where the fate of mankind rests in your hands.
In 2013 the world was devastated by an apocalyptic event, annihilating almost all mankind and turning the earth’s surface into a poisonous wasteland. A handful of survivors took refuge in the depths of the Moscow underground, and human civilization entered a new Dark Age.
The year is 2033. An entire generation has been born and raised underground, and their besieged Metro Station-Cities struggle for survival, with each other, and the mutant horrors that await outside.
Double-check that you don’t already own the game on Epic via their past giveaways before purchasing on Steam