about Fragment shader

I have a question about shaders in Unity.
I’m a beginner, so sorry if I’m asking something out of line…
I am currently considering implementing a VAT animation in VRChat based on the following article.
As I proceed, I would like to be able to set Metallic and Smoothness (and transparency if possible) in addition to the shaders in the article, but I would be very grateful if you could provide me with some reference articles and specific instructions on how to write shaders.
Reference articles↓

It looked like fragment shaders were being used,
I tried to do it while also looking at this article, but I’m stuck because I don’t know how to combine the two…
https://shop-0761.hatenablog.com/entry/2019/02/12/130000