I'm all about facial hair on guys, in fact that's my one-and-only, no exceptions rule- Must have facial hair, mustache minimum.
That being said, not every guy has a lot of facial hair. Some guys can't grow any at all.
Facial hair, whether it be a mustache, goatee, or beard, looks best when kept neatly trimmed. Not obsessively trimmed, mind you, just neatly so. As an example, Josey Scott*, former lead singer of the band Saliva-
www.youtube.com/shorts/r_VB5SfB-HY His beard trimming is on point, but I can't stand it when guys over-trim their mustaches like that, to the point that I want to yell at them "EITHER GROW A MUSTACHE OR DON'T GROW ONE, BUT QUIT DOING THAT HALF-ASSED MINI-MUSTACHE THING!". Of course I don't do that because it's their upper lip and therefore their choice how much of it they shave, but you get the idea.
I tend to go for mustaches more like this one-
i.pinimg.com/originals/da...c7ffc4d4a4e990aeae290.jpgBut I do realize that might be a bit much for most people. I'm sure there's a happy medium to be reached somewhere between Josey Scott and Derek Smalls.
The most important thing about facial hair, though, is that it feels GREAT on sensitive areas, so let your imagination go wild on the implications of that statement and whatever you come up with will probably be correct.
* Josey's accent is quite close to my own, if you were wondering.