What makes some metals shine?

Dislocations in the crystal structure. Here's a demonstration using a raft of small bubbles to simulate atoms in a metal (actual demonstration starts at 5:12 if you want to skip the introduction):

https://www.youtube.com/watch?v=sn1Y6zIS91g

You can see the same grains forming as the bubble raft is deformed.

That's hot dipped galvanized steel. The zinc crystal pattern formed on it is a called spangling.

https://www.steelmillsoftheworld.com/activities/datacenter/G...

It shines like that, with only some of the crystals being lit up at a given view and sun angle, from the surface being anisotropic. Light reflects more mirrorlike if it bounces parallel to the grooves in each of the individual crystals, and it is scattered if it bounces perpendicular to the grooves.

I think there's also an oxide layer contributing some iridescence, essentially a thin layer can cause constructive and destructive interference depending on light wavelength and thickness. If the light bounces mirrorlike, then a fraction of light bounces off the oxide surface, and a fraction transmits, then bounces off the metal. Depending on wavelength, these two light packets will interfere constructively or destructively. It depends on how many extra wavelengths the transmitted light travels (which depends on layer thickness, reflection angle, and light wavelength).

That particular photograph is probably edited.

The grains you see in a steel item are just grains of steel. Each grain has a particular crystalline structure, and neighboring grains have different structures or different orientations.

Most other metals lack a visible grain structure because they are purer (and therefore less likely to crystallize) or the metals in the alloy do not produce as many variations in grain structure.

This texture very often is the result of galvanizing the base steel to prevent/reduce corrosion: coat it with zinc so it "rusts" preferentially to the iron base metal. Similar to a sacrificial anode on a boat: "here, seawater, you need to eat something, so eat this chunk of zinc instead of my fancy bronze bolts/steel hull/etc"