Just a few tweaks that might be of use to you if you're playing this on the PC.
There's only one file that contains any editable information that has an affect on the game, and it's located in C:\Users\ YOURNAME\AppData\Local\4A Games\Metro 2033. Make a copy of the file inside (user.cfg) incase you fuck it up! Open the original file in notepad.
VSYNC The first one you should change is the vsync option about 14 lines from the bottom. Changing it to " on" doesn't have the effect you would expect (locking the frame rate at 30 or 60), but rather seems to unlock the frame rate, allowing the game to run a lot smoother. It's also rumoured to disable all 3D effects/processing, thus freeing up resources for those not running the game in 3D. FOV The second one you might like to change is the sick_fov option, again just a few lines from the bottom. This setting actually refers to the vertical FOV, not the horizontal, that's why it's currently set at lower figure than you might expect ( 45). Changing it to 60 seemed to work best for me, giving a much wider FOV more suited to the PC. I don't have a "before" screenshot with the original FOV, but here's one after setting it to 60.
GLOBAL ILLUMINATION The last settings that have a significant effect on performance are for global illumination. You can find 5 settings related to this about 20 or so lines above the vsync option. They are as follows: r_gi 0 r_gi_distance 16. r_gi_intensity 2. r_gi_overlap 0.5 r_gi_quality 0.4
Setting r_gi to 1 didn't make a difference for me, but some people have reported that it looks better and also performs better on high-end CPUs, especially when running in DX10 or 11. Altering the other variables definitely does something, because setting the r_gi_quality to something much bigger then 0.4 resulted in a huge FPS drop on my machine, but I couldn't see a difference in quality. It should be noted though, that even if you do get slightly better performance from switching this on, it actually causes some light flickering from certain light sources, and also doesn't seem very fond of red lights or laser sights, causing them to look a little bit buggy.
I went through every single other setting in the user.cfg file, and I didn't come across any others that seemed to impact performance at all. There are a few obvious ones of course that relate to settings you can change in game (MSAA and AF), but most of them didn't seem to do anything so I left them be. If you've had any luck with any of the other settings, feel free to share them here. There are also two DX11 references for depth of field and tesselation (r_dx11_dof 1, r_dx11_tess 1,) that I couldn't test as I don't have a DX11 card, but they appear to be just on/off switches for those effects.