Command key will only generate math symbols, not perform standard commands.

Hello emelia154, 

It sounds as though you’re noticing different characters appear versus performing the command you desire when using the Command key in conjunction with a letter. Apple Support Communities is a wonderful place for help! 

It sounds as though you verified that Sticky Keys isn’t enabled in System Preferences > Accessibility > Keyboard > Hardware. That is a great step, and we’re glad you had the chance to verify those settings. 

Since having this issue have you restarted your Mac? If not, restarting can help with resolving this issue. To restart your Mac please click the Apple logo towards the top-left, followed by Restart in the menu that appears. 

If you continue to have issues after restarting, can you let us know if the issue occurs in multiple apps, or one specific app? If the issue is specific to an application such as Pages or a Word, do you notice if it happens when you create a new document? 

You may also find the following article helpful as it lists a variety of shortcuts that can be enabled and used with the Command key. 

Mac keyboard shortcuts

We also recommend verifying the correct keyboard is set for Input Sources. This setting can be found in System Preferences > Keyboard > Input Sources.

We look forward to your response!

It sounds like your Command key is behaving as if it were the option key. Double check those modifier key preferences again. What does the option key do with c and v?

Try an external keyboard to see if the same thing happens.