Yerbas literally translates to "herbs," but in the context of this song, and especially with the adjective "malas" (bad), it refers to "weeds" or "bad habits."
Marc Seguí sings, "Sin tus lluvias se han secado mis malas yerbas" (Without your rains, my bad weeds have dried up). This metaphor suggests that the person's presence (the "rains") nourished his negative aspects or struggles, and now that they're gone, those issues are withering away. It's an interesting and unique way to describe personal growth or the impact of a relationship.
Marc Seguí and Don Patricio team up for "Malas Yerbas," a track that's all about the messy aftermath of a breakup. It's a story of trying to move on when your ex still has a hold on you, even if you know they're no good. The title, which means "weeds," is a great metaphor for a toxic relationship that just won't die, even when the "rains" (the good times) have dried up.
Our singer is caught in a loop, saying, "Te quiero / Como los pobre' al dinero" [I love you / Like the poor love money], but then immediately adding, "Pero me rompiste entero / Y no quiero que vuelvas más" [But you broke me completely / And I don't want you to come back anymore]. It's that push and pull of still having feelings but knowing it's over. He's trying to act tough, even saying he'll be with someone else if she doesn't call, but you can tell he's still hurting. Don Patricio comes in with a similar vibe, talking about how he knows her "de noche" [at night] but she doesn't wait for him anymore, and how other people have erased her footprints. It's a really honest look at the struggle of letting go.