  The light scalar field with a coupling to standard model particles provide a
possible source of the dark matter, long-range Yukawa forces or violation of
the weak equivalence principle, which can be potentially explored by precision
gravity experiments. We describe the searches for such light scalar fields with
the three types of gravity experiments, including the $G$-measurement
experiments, Inverse-Square Law (ISL) experiments, and equivalence principle
experiments. We investigate the potential influences of the scalar field as a
function of its mass, and focus on the experimental constraints from
torsion-balance gravity experiments. HUST-18 $G$-measurement torsion-balance
experiments place bounds on the photon coupling and electron coupling at up to
$\Lambda_{\gamma}=7\times10^{17}$ GeV and $\Lambda_{e}=1\times10^{17}$ GeV in
the mass ranges $10^{-9}-10^{-4}$ eV. Results from the ISL experiments by the
Universities of Washington, Stanford, IUPUI, HUST, Colorado, Irvine, Yale and
others allow us to set limits on the photon coupling and electron coupling at
up to $\Lambda_{\gamma}=5\times10^{17}$ GeV and $\Lambda_{e}=3\times10^{16}$
GeV for scalar field mass ranges between $10^{-5}$ and $10^{-1}$ eV.
Additionally, we also discuss the limits from equivalence principle
experiments, and $MICROSCOPE$ final result updates the constrains on the
coupling parameters at up to $\Lambda_{\gamma}=7\times10^{22}$ GeV and
$\Lambda_{e}=4\times10^{21}$ GeV for mass ranges $\lesssim 10^{-13}$ eV. These
results contribute experimental constraints to relatively unexplored mass
regions of {light scalar field} parameter space and improve upon previous
limits in some mass ranges. This work paves the way for long-range Yukawa
forces mediated by light scalar fields in future high-precision gravity
experiments.
