\documentclass[border=0mm]{standalone}
\usepackage{fontspec}
\setmainfont{TeX Gyre Pagella}
\usepackage{luamplib}
\mplibtextextlabel{enable} % <-- added option
\begin{document}
\begin{mplibcode}
beginfig(1);
  for x = 0 upto 1:
    draw (80x,16) -- (80x, -68) withcolor 3/4[red, white];
  endfor
  for y = 0 upto 3:
    draw (0, -20y) -- (160, -20y) withcolor 3/4[red, white];
  endfor

  string s; s = "Hand gloves";
  draw s infont defaultfont  shifted (0, 0);
  draw s infont "phvr8r"     shifted (0, -20);
  draw TEX(s)                shifted (0, -40);
  draw btex Hand gloves etex shifted (0, -60);

  dotlabel.urt(s,                     (80, 0));
  dotlabel.urt(s infont "phvr8r",     (80, -20));
  dotlabel.urt(TEX(s),                (80, -40));
  dotlabel.urt(btex Hand gloves etex, (80, -60));
endfig;
\end{mplibcode}
\end{document}