system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 What is it specifically about substances like mercury and lead that kills you?

I understand something like Carbon Monoxide which physically takes up space that should have oxygen there but what about lead in my blood kills me? Is it a chemical reaction that steals nutrients? Does it puncture blood cells?
gpt
Many proteins in your body incorporate atoms/molecules of specific metals like iron, copper, manganese etc. Those metals are crucial to how those proteins function. Heavier metals, like mercury can be put into those proteins by mistake. This means the protein will no longer work. Depending on what the protein does normally, that can cause lots of problems.