Let $L$ be a line bundle on $X$. We say that a metric $\|\ \|$ on $L^{\rm an}$ is a model metric if there is a non-zero $d\in{\mathbb{N}}$ such that ${\|\ \|}^{\otimes d}$ is an algebraic metric on $({L^{\rm an}})^{\otimes d}$. By Proposition 2.8 and Remark 2.5, $\|\ \|$ is a model metric if and only if it is a piecewise ${\mathbb{Q}}$-linear metric.