Metal Bringer uses a Pixelation filter which works based on render resolution.

The Steam Deck has a 1280x800 resolution, which leads to extremely large pixels and the effect even bugs out around the character.

To fix this:

1) In the Steam Library, long tap Metal Bringer

2) Go to Properties, General, and select Game Resolution and set it to 2560x1600

3) Launch Metal Bringer

4) Press the [...] button on the right side of the Steam Deck

5) Under Performance, toggle on Per-game Profile, toggle on Half Rate Shading, and set Scaling to Linear

6) Optional: Set frame rate cap to 30 fps for optimal performance.

7) From the main title screen, go to video options in-game, set resolution to 16:10, then select Full Screen.

8) Optional: Set Shadow Quality to Low and turn off Anti-aliasing.

These changes will make the pixel size significantly smaller, making the game look much clearer. Half rate shading will reduce the performance impact of the higher rendering resolution. The other settings will help keep a stable 30fps, since Metal Bringer dips below 60fps when many enemies are on screen regardless.