The Munis was known as the custodial corps of Lorien's workforce, they were mostly involved in maintenance work.
Citizens of Lorien were selected for Munis service by lottery, no more than twice in their lifetimes. Those chosen for Munis service serve a term of a year. The Munis also offer apprenticeships, an option given to Sandor when he is expelled from the Lorien Academy. There is no shame in performing Munis service but this was not something Sandor felt he was suited to.
The full extent of the Munis competences are not known, although it is known that The Grid's main function is to monitor the goings on in the Capital and compile information on the flow of goods and people for the Munis to keep everything running smoothly.
During the Mogadorian Invasion of Lorien, a Munis vehicle was parked outside the the wreckage of The Chimæra and it's driver was seen attending the victims. All transmissions on the planet were dedicated to Munis communications about rescue efforts.