I run SKS Edge Al metal mudguards on my gravel bike- I use the 46s with 42 or 40c tyres. I do around 70 miles a week on that bike, half on and half off road, and once a week head out to the hills and ride single-track on it that o also enjoy riding on my mountain bike.
They’re excellent. I’ve had plastic guards snap and cause all sorts of problems but these are just so robust. I never take them off and they have a sort of emergency quick release where the stays attach to the guard in case you got a stick in them.
Once that come off easily I don’t find provide enough coverage, aren’t very stable and look awful.