In the present paper, the mean signal value and its fluctuations were investigated for the well known Micro-Mesh Gaseous Structure (Micromegas) filled with argon-based gas mixtures. The number of primary electrons and ions in the conversion gap were calculated using the FLUKA code for incoming electrons. The signal resolution is a function of the energy loss or the number of produced primary electrons and its fluctuation in the detector volume. The signal generations were made with a Single Particle Monte Carlo simulation technique in the amplification gap region. We assumed a homogeneous electric field inside both the conversion and the amplification gap because the electric field shows only a small change near the openings of the microgrid. Based on the simulation, we discuss the signal fluctuations that affect the work performance of the Micromegas for different argon-based gas mixtures.