If the government imposes a maximum price for milk that is above the equilibrium price:

Maximum prices in economics can be also known as Price Ceiling, where it is the legal maximum prices that producers can sell their good at. However, as this causes a market disequilibrium, ceteris paribus, there will exist a surplus of goods produced. This is due to the signalling and incentive effective on producers and consumers resulting in the increase of price (that has been set by the government). Consumers would consume less of the product as it is more pricey than before, hence they are less willing and able to buy the product at the new price. Producers on the other hand sees more revenue to be earnt through higher prices and hence would devote their resources into producing that product. Hence the mismatch of supply and demand results in a surplus of products and would likely result in the government buying all the surplus out of interest for producers.