Metals and glass are highly recyclable but you’re right to question coatings. Dyes in the glass make it a challenge as well; green, clear, and brown glass are relatively common and sortable. Some areas sort their glass this way. The unpredictability of the chemical composition of the glass means it’s not made into the “same thing”, but moves down a grade. Like paper - the brown paper towels are a downgrade from the original product that was recycled to make them.

Aluminium cans are highly recyclable but if they’re shrink wrapped or have a label it can make it not worthwhile. https://www.aluminum.org/news/aluminum-container-design-guide-outlines-four-keys-circular-recycling

Metals like steel are also recyclable but the value does drop off because it’s not really possible to ascertain the grade or alloy or type of metal with high degree of certainty. Fortunately there’s plenty of applications for metals in that category.

Lead from car batteries is almost entirely recoverable.

Still, I’ve been wondering. I’ve come to learn that plastic recycling is largely a myth/scam, but what about glass and metal recycling?

They recycle fine but they still need a lot of energy to be recycled. Energy is the main issue here: energy needs to be extracted/produced which has a huge environmental cost (even solar/wind turbines have an environmental cost, as well as has their maintenance). So, the best thing we can do, as consumers, everyone of us at our humble level, in our everyday live, would be to consume as little as we can of everything. To create less waste, we should buy less, which would also mean we would need to waste less energy, a lot less, to recycle whatever can be.

Plastic recycling is still superior to discarding, but inferior to avoiding in the first place. It is simply energy intensive and not many people do it.

Glass, steel and aluminum recycle nicely. Copper can’t be separated from steel when it’s molten down together so avoid mixing these. Plastic coatings just burn down in furnace