A ceiling grid system formed of struts has a plurality of elongate insert light units. The grid system suspended from the ceiling and comprising a multiplicity of steel elongate channels (struts) arranged in the grid. The channels having a downwardly directed U-shape and defining an opening and an open channel interior, the channel having opposing J-shaped wall portions, each wall portion with an inwardly directed curved lip portion defining a gap width therebetween the two wall portions. The elongate insert light units seated within one of the steel elongate channels, each insert light unit having an elongate body with a light emitting side, each insert light unit comprising a housing, and a strip of light emitting diodes, and a transmission portion at the light emitting side, the body retained in the interior of the channel, each light unit removable and replaceable with the respective channel.