Hellooo I created this very easy to follow YouTube tutorial showing how you can quickly texture paint a gold or any other metallic surface in Blender by using the Fill tool and a Gradient Map
Please watch the video or read a mini guide below
First import a reference picture of a gold bar, this one was found on Wikipedia
Open up the Texture Painting tab and select Fill as the paint mode on the left hand side of the window, then on the right hand side under color palette you can create a new palette and select light and dark shades from the reference image using the color picker eyedrop tool
Then choose Gradient as your color method on the right hand side and add color stops by selecting the + symbol and selecting the colors from your palette so they go from dark to light to dark and light again.
Now you can drag the curser over your 3d opbject and it will be given the metallic gradient you created as well as adding it to the UV texture map.
I hope you found this guide useful? If so please follow my blog, like and subscribe to my YouTube channel to recieve more 3d tutorials in the future.