How do I fill this hole in outdoor post

Hi. We had some changes made and the upshot is that I now have a post with several holes in it, and I have no idea how to fill the holes before repainting.

The post is 90mm galvanised steel, wall thickness about 3mm (guessing). The holes are about 10mm diameter.

This spot is fairly visible so I want the job to be aesthetically good (ie no lumps or bumps on the post if possible. I can imagine most fillers would fall out some time in the future, given there is so little for them to cling to.

Any ideas how I should do this
Thanks
Arron

Edit, for some reason I can’t upload a picture. Just imagine a painted 90mm galvanised post with several 10mm holes in it.
Cheers

fill the holes with weld and grind/linish them smooth.could you tap a thread and put an m10 grub screw in there to give the filler something to grip to?

Have previously reused a lot of duragal RHS left over from a pergola, I just used the mig to fill and then ground back.Only other option I can think of is something like JB Weld but have never used it that way myself.

Thanks for the replies. I’m reluctant to weld due to the location problems and my mediocre skills. I do like the idea of JB Weld though. Considering this is non-structural, not stressed, not heated and will be protected from UV by paint then I think it’ll be ok.

I have also noticed that after I weld things they rust a lot.

I’m thinking I may design something which I can 3d print, which will go through the hole, press against the other side and screw up tight, so it forms a flush backing for the hole. Just to get a solid surface to fill against with the JB Weld. The plastic thing can stay there but won’t play any role other then helping me fill it. Is that a good idea?

Cheers