as a determiner (before a noun): Most shops will be closed over the Christmas holiday. (after ‘the’): Which athlete won the most medals?
Don’t use most of before a noun when there is no article or possessive before the noun. Use the pattern most + noun :
✗ Most of banks want to have more and more customers.
✓ Most banks want to have more and more customers.
✗ Most of information on the Internet is written in English.
✓ Most information on the Internet is written in English.
Explain to me, please, why is the article before "most medals".
You need to understand the difference between "most" and "the most."
Take this as an example: If we said that the Steelers have won most Super Bowls, that would be saying that they have won a large majority of them. That is not true. They have won 6 Super Bowls, out of 48 that have been played.
If we say the Steelers have won the most Super Bowls, that is true. No one has won more than they have. They are the only team to have won 6.
I think you mean "Macmillan dictionary says about using 'most':"
We don't say that books "are saying" something, even if they're online. If something has been edited you can say, "This dictionary said X yesterday; now it's saying Y".