I am very happy with the prints that I have had made by "Print to Metal" in Victoria.
https://www.print2metal.com/
I went with these guys because they had a good reputation when I queried metal printing. I have used them to produce astro print gifts for family and the work is excellent in my opinion. They can handle big files, no need to reduce size, or go to jpgs. Give them a call.
For just producing things to hang on the wall, i find that it really helps the end result to go with bright or contrast images. More discrete images that look good on your screen may not look as good when printed (without backlighting). I have a metal print of the Vela Remnant in narrowband, which is amazing on my big editing screen, but after printing on metal and hanging on the wall, it looked pretty drab. The solution was to use a gallery light, which changed it completely, it really pops off the wall now. So how you display it can make a big difference.