  We present a careful and detailed light curve analysis of publicly available
$I$-band data on fundamental mode RR Lyrae (RRab) stars of the Large Magellanic
Cloud (LMC) obtained by the Optical Gravitational Lensing Experiment (OGLE)
phase-III project. Using the Fourier parameters of $13,095$ RRab stars,
metallicities and absolute magnitudes of individual stars are obtained. The
representation of stars on the $P-\phi_{31}^{V}$ plane shows the existence of
three significant metallicity groups with mean metallicities as $-1.20 \pm
0.12$ dex, $-1.57 \pm 0.10$ dex and $-1.89 \pm 0.09$ dex. The corresponding
absolute magnitudes of these three groups are obtained as $0.70\pm 0.08$ mag,
$0.59 \pm 0.06$ mag and $0.49 \pm 0.08$ mag, respectively. Distribution of
these three groups as a function of vertical $|z|$ distance indicates that the
formation of the LMC disk predates the formation of the inner halo. Issue of
the existence of a metallicity gradient as a function of galactocentric
distances has also been addressed.
  Approximating the structure of the LMC disk as a triaxial ellipsoid, the
inclination angle ($i$) relative to the plane of the sky and the position angle
of the line of nodes ($\theta_{lon}$) were estimated as $24^{\circ}.20$ and
$176^{\circ}.01$, respectively. The axes ratios and the eccentricity were also
determined using the principal axes transformation method.
