The Muon Spectrometer of the ATLAS detector has recently undergone a major upgrade in
preparation for operation under experimental conditions foreseen at the High-Luminosity LHC
(HL-LHC). Two New Small Wheels (NSW) have been constructed and installed to replace the
innermost muon station in the high-rapidity regions of the ATLAS detector. This new system
is designed to provide improved muon trigger momentum resolution and fake rate rejection in
the forward region of the detector, to maintain the current ATLAS physics capability under the
higher background environment of HL-LHC. The NSW has an active area of more than 2400 m$^2$
and is equipped with multiple layers of two novel detector technologies: small-strips Thin Gap
Chambers (sTGC) and resistive Micromegas (MM). With such a large active area, the ATLAS
NSWs are the first large-scale use of Micromegas technology in high-energy experiments. The
latest results from the commissioning of the NSW in preparation for the LHC Run-3 data-taking,
as well as initial performance measurements, will be shown.