This article is enlightened with comparison screenshots.
Changing the FOV is simple: navigate to C:\Users\[user]\AppData\Local\4A Games\Metro LL, enter the folder labeled with a bunch of random numbers and letters (e.g. 110000103249C0e), and open the user.cfg file with Notepad. Once inside, hit Ctrl + F and search for “fov” to find the r_base_fov 50.625 line: 50.625 represents the default FOV. To alter it, simply replace the value with one of your liking (e.g. 60), save the file, and boot the game.