When Playing together with Metal and Stars the game fails to get past the loading screen. Upon reaching 50% and transitioning from "Cropping Bitmaps" to "Loading Sprites", the game just closes without an error output. Opening the factorio-current.log only has 3 errors which say that "Prepared sprite registrations are empty" and "No pictures to put in atlas" followed by an error about a failure to display the message dialog (I assume this is where the error should normally be thrown on the screen).

Are both of them the latest versions?

Both mods are using their latest versions as of writing this comment.
Better Starmap Background - 1.1.3
Metal and Stars - 0.1.6

I'm getting the same issue, but I'm loading a lot of mods (just testing for a new multiplayer save).

These are the planets I'm loading:
Cerys
Corrundum
Cubium
Factorio and Conquer: Tiberian Dawn
Lignumis
Moshine
Muluna, Moon of Nauvis
Planet Castra
Planet Maraxsis
Secretas&Frozeta
Tenebris Prime

I'm using this mod to adjust the solar system: Organized Solar System

This is the error in the log:
10.134 Error AtlasBuilder.cpp:157: Prepared sprite registrations are empty: start = 16057, to try = 0, max size = 4096, registered sprites count = 323124
10.134 Atlas: virtual = 0, flags = none
10.134 registration[16057]: padding = 1, dest_width = 4096, dest_height = 4096, filename = Better_Starmap_Background/graphics/icons/starmap_background_star_01.png
10.134 registration[16058]: padding = 1, dest_width = 4096, dest_height = 4096, filename = Better_Starmap_Background/graphics/icons/starmap_background_star_02.png
10.134 registration[16059]: padding = 1, dest_width = 4096, dest_height = 4096, filename = Better_Starmap_Background/graphics/icons/starmap_background_star_03.png
10.134 registration[16060]: padding = 1, dest_width = 4096, dest_height = 4096, filename = Better_Starmap_Background/graphics/icons/starmap_background_star_04.png
10.134 registration[16061]: padding = 1, dest_width = 38, dest_height = 16, filename = space-age/graphics/terrain/space-platform/tile-animations/north-top.png
10.134 Error Util.cpp:81: No pictures to put in atlas.

Maybe you can try this: In the graphics settings, atlas texture size needs to be set to 8192 or 4096？

It doesn't help, no matter what value you set, the error still appears "No pictures to put in atlas"