In general waste glass and metals can be recycled easily and effectively and in many cases it is energetically efficient to do so compared to making new glass or metals form natural resources. There are a couple of caveats to this though that might be important:

• Not all kinds of glass can be recycled, the type of glass used for single use containers can be recycled though (soda-lime glass)
• Glass making currently does not work with pure recyclate (broken up reclaimed glass), but 50% recycling material is possible and common
• colour defects in recycled glass are a problem, so make sure you know what colours of glass can be recycled by your local recycling company and how they need it separated. this is especially important for white glass and brown glass. some glass recycling processes don’t need colour separation though.
• ferrous metals, aluminium, copper, precious metals and many of their alloys can be recycled effectively and the percentage of products made from recycled metals is going up. for other metals its a bit more tricky: for example titanium is too niche to recycle from a consumer waste stream, lithium is hard to process from a waste stream in general, zinc is usually only recycled as a byproduct when recycling galvanised steel.
• There is also the issue that composite materials may not be fully recyclable. metal plated plastics are typically not recycled. tetra paks are only partially recyclable – the aluminium liner is typically lost because recycling it is not economical right now. the plastic liner in tetra paks is also typically lost – only the paper fibres are recovered.

There is a lot of research into metal recycling going on right now though, so that might change soon. :) Just because the technology exists to recycle something does not mean that somebody is doing it unfortunately. Even if it is economical to recycle something – meaning the recycled material would cost less than the virgin material – it is still possible that it isnt done because the market is too niche. For instance borosilicate glass can be recycled and it would be very energy efficient to do so but the market would be too small for anybody to invest in it. I guess energy is still too cheap.

Plastic liners in general are not typically recycled, if there is no easy method to separate them from the base material. This applies to cans, paper cups, metal bottles, furniture and lots of other things. In most cases they still allow the base material to be recycled though. For instance in ferrous metal recycling (cans) the plastic liners might simple be burned away in the electric arc furnace.

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.

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.

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