Shimmer effect on button?

Hello everyone, I would like to know how to make a shimmer effect if a button is hovered on.

But what I want to know is can I use a gradient moving across the button or an image?

If you look at the roblox homepage whilst it’s loading or I think youtube then it gives a gradient moving across a bar or something.

2i1 (2 in 1): How would I make a loading screen that has an image with color and a image without color but the image with color overlapses the colorless one and gives it color?