  Multi-hydrogen lanthanum hydrides have shown the highest critical temperature
$T_c$ at 250-260 K under 170-200 GPa. However, such high pressure is a great
challenge for sample preparation and practical application. To address this
challenge, we propose a novel design strategy for ambient-pressure high-$T_c$
superconductors by constructing new few-hydrogen metal-bonded perovskite
hydrides, such as Al-based superconductor $\rm {Al_4H}$, with better ductility
than the well-known multi-hydrogen, cuprate and Fe-based superconductors. Based
on the Migdal-Eliashberg theory, we predict that the structurally stable $\rm
{Al_4H}$ has a favorable high $T_c$ up to 54 K under atmospheric pressure,
similar to SmOFeAs.
