How do bank interests work?

I know i could probably just google it, but i find navigating through countless shitty bank websites that are most likely wording things in a way to appear better than the deal is actually is unpractical. Anyways i was talking to my friend who just inherited money averaging 2 million how he plans on just putting it in a bank and living off the interest rates which he tells me is 10% monthly, is that actually true? I always thought it was way lower than that and more complicated than just putting money and getting a monthly percentage relative to it.