Enmaquinado is a fantastic example of Colombian slang you'll hear in music. While it comes from the word máquina (machine), its slang meaning is 'to be geared up' or 'ready for anything', often implying being armed.
In the song, Feid says he arrived at his girl's house enmaquinado, por si las moscas (geared up, just in case). It's a powerful word that paints a vivid picture of his street-smart lifestyle and adds a layer of toughness to his romantic pursuit.
Feid is tired of being far away from the girl he likes, and even more tired of the rumors getting back to her family. Her mom is not a fan, and he knows exactly why: "Por las cadenas y por mis tatuajes / Porque ando siempre rodeado de bandidos" (Because of my chains and my tattoos / Because I'm always surrounded by thugs). He's got a bad-boy reputation, and her parents are worried. But Feid isn't trying to hide it. He pulls up in a big truck, ready for trouble, and makes it clear he's protective, warning that if anyone else touches her, "les cae to' el peso" (the full weight will fall on them).
Despite the tough-guy image, he's also trying to win over the family, sort of. He tells his girl to pass a message to her mom: "que algún día la saco del barrio / Y me la llevo pa'l Pobla" (that one day I'll take her out of the neighborhood / And bring her to El Poblado). El Poblado is a very nice area in his home city of Medellín, so he's basically flexing his success and promising to take care of them. He's rich, he's a little dangerous, and he's coming to pick her up to go party, telling her to sneak out the back.