SanDisk memory cards come already formatted but you can re-format them when you want to delete all data especially if you think a damaged file on the card is causing problems.

Unable to format SD card write-protected. SD card is loaded with bad blocks that make damage the SD card. Windows platforms can no longer erase a corrupted memory card.

If you're a keen photographer, you probably have a lot of memory cards that need to be wiped. Here's how to format SD and microSD cards safely within macOS.

I have a problem with my Rio PMP-300 mp3 player. It works fine except for the memory card.