https://www.pcgamer.com/metro-exodus-will-only-release-on-the-epic-store-but-steam-preorders-will-be-honoured/

Metro Exodus will release "solely" on the Epic Games Store when it launches on February 15, Epic and publisher Deep Silver have revealed today. This follows news from earlier this month where it was revealed The Division 2 was coming to Epic's store as part of a multi-game agreement with Ubisoft. 

If you have already preordered the game on Steam, you'll get to play it on there. Epic's exact words on that subject are that "any customer with an outstanding preorder for Metro Exodus on PC through any digital retailer will receive their game as expected."