  Let $\Omega$ be a domain on the unit $n$-sphere $ \mathbb S^n$ and
$\mathring{g}$ the standard metric of $\mathbb S^n$, $n\ge 3$. We show that
there exists a conformal metric $g$ with vanishing scalar curvature $R(g)=0$
such that $(\Omega, g)$ is complete if and only if the Bessel capacity
$\mathcal C_{\alpha, q}(\mathbb S^n\setminus \Omega)=0$, where
$\alpha=1+\frac2n$ and $q=\frac n2$. Our analysis utilizes some well known
properties of capacity and Wolff potentials, as well as a version of the
Hopf-Rinow theorem for the divergent curves.
