  Observations and statistical studies have shown that giant planets are rare
around M dwarfs compared with Sun-like stars. The formation mechanism of these
extreme systems remains under debate for decades. With the help of the TESS
mission and ground based follow-up observations, we report the discovery of
TOI-4201b, the most massive and densest hot Jupiter around an M dwarf known so
far with a radius of $1.22\pm 0.04\ R_J$ and a mass of $2.48\pm0.09\ M_J$,
about 5 times heavier than most other giant planets around M dwarfs. It also
has the highest planet-to-star mass ratio ($q\sim 4\times 10^{-3}$) among such
systems. The host star is an early-M dwarf with a mass of $0.61\pm0.02\
M_{\odot}$ and a radius of $0.63\pm0.02\ R_{\odot}$. It has significant
super-solar iron abundance ([Fe/H]=$0.52\pm 0.08$ dex). However, interior
structure modeling suggests that its planet TOI-4201b is metal-poor, which
challenges the classical core-accretion correlation of stellar-planet
metallicity, unless the planet is inflated by additional energy sources.
Building on the detection of this planet, we compare the stellar metallicity
distribution of four planetary groups: hot/warm Jupiters around G/M dwarfs. We
find that hot/warm Jupiters show a similar metallicity dependence around G-type
stars. For M dwarf host stars, the occurrence of hot Jupiters shows a much
stronger correlation with iron abundance, while warm Jupiters display a weaker
preference, indicating possible different formation histories.
