"He drinks milk."
Translation:Il boit du lait.
There are 2 reasons why il aimes du chocolat is not correct:
the conjugation in 3rd person singular never has an -s: "il aime".
the direct object of an appreciation verb is automatically preceded by a definite article: "il aime le chocolat". The reason is that when you like or dislike something, you like or dislike it all or the whole category. Therefore, the sentence becomes a generality and generalities in French require a definite article: "il aime la soupe ("soup" in general), les chansons ("songs" in general).
Appreciation verbs are: aimer, adorer, apprécier, préférer, détester, haïr, respecter