"Hurry up! I don't have much time before the flight leaves! Also, why did you pack so many suitcases for a two-day trip? At least we have a lot of snacks for the road."

much: Used with uncountable nouns (like time), especially in negative sentences and questions. (Notice that "a lot" is incorrect here because it is missing the word "of").

many: Used with plural countable nouns (like suitcases). We often use "so many" or "too many" to emphasize a large number.

a lot of: Used with both countable and uncountable nouns, most commonly in affirmative (positive) sentences.