What happens when my SSD’s health meter reaches “bad” or in the “red area”?

The drive will become read-only.  Here's the explanation. Flash memory, which is used to store data in SSDs, has a certain writing limit. To be more accurate, it has erasing limit, because data is erased only when it is written. SSD will not be able to write data when its lifetime is over, but it will be able to read data.   Thus, when the drive health reaches this state, you will have a read-only drive.  You will be able to read all your data, but you will not be able to modify it. It is strongly recommended that you replace your SSD when its health gets as low as 90% to 95% bad health.