Depends on the hardness of the metal you would need a metal. These stoves are mostly aluminium oxide, which has a mohs hardness of 9 and steel is 4-8. I looked more into it and I found glass ceramic stoves have a mohs hardness of 6-7. So a very hard steel should be able to scratch it, but most steels including stainless should be fine.

Glass is harder than most metals.

It can, yeah. You have to be careful to press gently in the center of the blade and not put pressure on the corners which will gouge huge scratches into glass. I have one of these for cleaning my paint pallette and get double-duty out of it on oven cleaning day.

They make cleaning kits for these stove tops that typically come with a cheaper plastic version of the tool with a weaker metal razor. Still does the job well, but less scratching chance. Also usually comes with a fine-grain polishing cream and sponges to apply it with. The cream helps to buff out lighter scratches and remove some of the cooked on stuff.

It doesn’t scratch the glass, even when applying quite some force. The blade dulls pretty fast, it probably doesn’t have the hardness to damage the glass.

It’s specifically called a [glass/ceramic] stove cleaning [blade/scraper]. I’ve used one a lot and it doesn’t seem to do noticeable damage (glass stove tops need to be pretty tough anyways to handle regular cooking)

As long as you keep the blade flat against the glass it doesn’t scratch. If you use the corner of the blade to scrape it will scratch.