Macheath is basically an all round criminal - definately a murderer- for profit - thief (along with his gang they steal the furnishings and food for his marriage to Polly), probably a rapist, maybe a pimp and possibly a bigamist. But whatever activity he does it is all for his own benefit. Which is one of the difficulties when performing "The Threepenny Opera" - how do you make such a disreputable and dislikeable character sympathetic to an audience? Or instead do you not try?
Fantastic musical - I played Lucy Brown in it once and loved it - get to come on in the second act sing two briliiant songs ("The Barbara Song" - somethimes sung by Polly but can be sung by Lucy - and the "Jealousy Duet") - then back on for the finale.
Btw in the show the song is sung by the Ballad Singer as an introduction to the show and to Mack's character