many只能修饰可数名词的复数;a lot of既可以修饰可数名词,也可以修饰不可数名词。much一般是用在疑问句和否定句里；而a lot of常用于肯定句中。
many和a lot of的区别
一、指代不同
1、many：许多的。
2、a lot of：很多。
二、语法不同
1、many：many用作形容词时后接复数名词,表示许多同样的人或物(但数目不明确),用作主语时,其谓语动词要用复数形式。常用于否定句中。
2、a lot of：lot的基本意思是“许多,大量”,在肯定句中常用于alotof或lots of结构,可修饰可数名词,也可修饰不可数名词。其含意与many或much相同。
三、侧重点不同
1、many：many是普通用语,其后只能接可数名词复数。
2、a lot of：a lot of和lots of既可接可数名词,也可接不可数名词,多用于肯定句。
many和a lot of例句
1、Many people, many tastes.
2、Many Wells, many buckets.
3、Many dishes, many diseases .
4、You've met many, many people.
5、Many, many happy returns of the day
6、raise (a lot of) eyebrows
7、That’s a lot of dough.
8、There are a lot of people, a lot of flowers, a lot of candles and food.
9、I always want a lot, a lot of love.
10、a great number of ; a lot of