Non-collinear antiferromagnets are currently an area of much active research due to their potential use in creating robust spintronic and spin memory devices. We have recently been carrying out in-depth studies of spin-waves (via inelastic neutron scattering (INS)) of various insulating non-collinear antiferromagnets such as (Y,Lu)MnO3, PdCrO2, and CuCrO2 to find unusual effects such as magnon-magnon and magnon-phonon couplings. Our immediate question is now how these effects change for metallic systems with noncollinear ground states. Mn3Sn is one such example with an antiferromagnetic ordering at 420 K, and, more importantly, has been recently found to exhibit anomalous Hall effect, which can arise from Berry's phase. In this proposal, we propose to study the spin dynamics by taking advantage of our large single crystal and understand the underlying physics.