\documentclass{standalone}
\usepackage{luamplib}
\begin{document}
\begin{mplibcode}
beginfig(1);
  string s; s = "\TeX\ sets maths like this $e=mc^2$";
  draw ("1. " & s) infont defaultfont;
  draw ("2. " & s) infont "texnansi-lmr10"  shifted 20 down;
  draw ("3. " & s) infont "cmtt10"          shifted 40 down;
  draw ("4. " & s) infont "texnansi-lmtt10" shifted 60 down;
  bboxmargin := 14;
  picture p; p = currentpicture; 
  fill bbox currentpicture withcolor (1,1,31/32); 
  draw p; draw bbox p;
endfig;
\end{mplibcode}
\end{document}
end.