I would never say  �There �s much milk �
I would say  � Is there much milk? � Yes. There �s plenty. or Yes there �s a full bottle/carton.
No. There �s not much. or Not a lot.
 
More uses:
 
Of someone who is sick:
His condition is much improved. (formal)
He is much better. (more casual)
 
Often used for comparison:
He �s a much better musician than I am.
He practises much more than I do.
You �ve got much more patience than I have.
They have a much bigger house than we do, so we are having the party there .
 
There are many ways to approach this problem. 
He �s tried many different treatments for his skin complaint.
These have a more formal sound than 
He �s tried lots of different treatments.