"people", when used as the plural of "person", requires a verb form that's also in the plural. In your example, "most people" refers to multiple individuals, so you need the plural.
Unrelated to your example, but useful to know: the word "people" could also be used as a singular noun, but with a different meaning - it refers to a group of human beings with a common culture, tradition, language, etc:
Americans, as a people, value hard work and not giving up easily.
It also has its own plural:
The peoples of South America, one of which was the Incas, had rich cultures and complex belief systems.
Most of the time, however, you'll see "people" as the plural of "person" or "human being".
1You don't have to capitalize insulin. – snailplane – 2016-03-03T00:34:48.097
@snailboat, you're right, I edited it. – Judicious Allure – 2016-03-03T00:37:39.527
1I have related question and when I was googling this came up. How should I say correctly 'most of the developers know' (or knows)? To me 'know' is the correct form. I'm reviewing a blog by non-native speaker and he used 'most of the developers out there knows' which seems wrong to me. I'd say 'most developers know' and drop the 'of the ' and knows. What do you think? – Naomi – 2017-11-28T18:16:21.293
1@Naomi Most of plural (=developers for example) is always plural. Most of singular (most of it goes to the sea) is always singular. So you can conclude that the correctness depends on what you're referring to, when you're mentioning 'most'. – Judicious Allure – 2017-11-28T20:36:01.337
3Ask yourself: How many are "most"? More than one? You should drop the article, btw. – Stephie – 2015-03-08T05:24:31.133
Have a look at OALD, most no. 2. - most verbs are reguar - and note the remark about "the". – rogermue – 2015-03-08T06:52:32.823