  We interpret the recent excess in a rare decay of the Higgs boson, $H\to
Z\gamma$, using a light axion-like particle (ALP) in the mass range less than
0.2 GeV. The dominant decay of such a light ALP is into a pair of photons,
which are very close to each other, such that it mimics a single photon in the
ECAL detector. It can explain the excess with a coupling $C^{\rm eff}_{aZH} /
\Lambda \sim 4 \times 10^{-5}\;{\rm GeV}^{-1}$. A potential test would be the
rare decay of the $Z$ boson $Z \to a H^* \to a (b \bar b)$ at the Tera-$Z$
option of the future FCC and CEPC. However, it has a branching ratio of only
$O(10^{-12})$, and thus barely testable. The production cross section for $pp
\to Z^* \to a H$ via the same coupling $C^{\rm eff}_{aZH} / \Lambda$ at the LHC
is too small for detection.
