September 23 (SeeNews) - The blue-chip index of the Belgrade Stock Exchange, the BELEX15, rose on Monday, boosted by gains in cookware maker Metalac [BEL:MTLC], oil and gas company NIS [BEL:NIIS], insurer Dunav Osiguranje [BEL:DNOS], and industrial gases producer Messer Tehnogas [BEL:TGAS], bourse data showed.