Montgomery, 30 has been with Sheffield United since he came through the youth ranks at the Lane and made his first professional game as a substitute in a 4-2 defeat at Norwich City in October 2000 and has since 319 (+79) league and cup appearances and scored 11 goals for the Blades.
He joins Kenny Jackett's Millwall in the Championship who Danny Wilson says will 'gain experience.' He has been pushed out of the team since the arrivals of Kevin McDonald and Michael Doyle and Monty could make his Lions debut at Doncaster Rovers tomorrow night.