  Giant low-surface brightness (GLSB) galaxies are an extreme class of objects
with very faint and extended gas-rich disks. Malin 1 is the largest GLSB galaxy
known to date, but its formation is still poorly understood. We use VLT/MUSE
IFU spectroscopic observations of Malin 1 to reveal, for the first time, the
presence of H$\alpha$ emission distributed across numerous regions along its
disk, up to radial distances of $\sim$100 kpc. We made an estimate of the dust
attenuation using the Balmer decrement and found that Malin 1 has a mean
H$\alpha$ attenuation of 0.36 mag. We observe a steep decline in the star
formation rate surface density ($\Sigma_{\rm SFR}$) within the inner 20 kpc,
followed by a shallow decline in the extended disk. Similarly, the gas phase
metallicity we estimated shows a steep gradient in the inner 20 kpc, followed
by a flattening of the metallicity in the extended disk with a relatively high
value of $\sim$0.6 $Z_{\odot}$. We found that the normalized abundance gradient
of the inner disk is similar to values found in normal galaxies but with an
extreme value in the extended disk. A comparison of the star formation rate
surface density and gas surface density shows that, unlike normal disk galaxies
or other LSBs, Malin 1 exhibits a very low star formation efficiency. Owing to
the detection of emission lines over a large part of the disk of Malin 1, this
work sheds light on the star formation processes in this unique galaxy,
highlighting its extended star-forming disk, dust attenuation, almost flat
metallicity distribution in the outer disk, and exceptionally low
star-formation efficiency. Our findings contribute to a more detailed
understanding of the formation of the giant disk of Malin 1 and also constrain
possible proposed scenarios on the nature of GLSB galaxies in general.
