General Mills is a large food company that produces the favorite cereals you eat today, Lucky Charms, Cheerios, Trix, etc, basically they make everything in General hence their name.
Continuing with the theme of Serial Killer & Cereal I go on to say, “Haven’t made a Mill but yo Trix ass rap about it like it’s General” I’m referring to the upcoming rappers who talk about the glitz and the glam like it’s the life they are living as of now, in which they aren’t, they just some MF-ing Trixs rapping bout Mill(millions of dollars) like it’s general(something that pertains to them.