Which slot in urp lit shader do i put my texture for texture packing

At the bottom of Lit Shader | Package Manager UI website, it gives details about texture packing. My question is: after I have packed my texture, which slot in the URP Lit Shader should I put it in?

huh, good question, presumably you just plug it into the metallic map section, and it just uses the channels like that naturally?

I never tried it before.