So I'm modelling this sardine can with a logo on it... I have created my own logo as a png file and I want to apply it on a red metallic material... I have already tried applying it on the subsurface but it doesn't make much of a change
Ok so, what you have to do is tell the shader where to draw your logo and where to draw the metallic part. If your lid is uv-unwrapped you can manipulate the uv coordinates to do it. Provided you have a png with an alpha channel this is quite easy. This is my setup :
Basically you take the uv coordinate and pass it through a mapping node to tweak the scale and position of your uvs. Then plug it to the image texture node and remember to set it to clip so that it doesn't repeat. Plug the alpha in the factor input of a mix shader and plug in the top input your metallic shader and in the bottom one your logo shader. Then tweak the mapping node as you wish.