The thickess in prepainted metal roofing is 0.6mm or what they call gauge 24. The higher the gauge the thinner is the metal. Common thickness are 0.4mm or gauge 26, 0.5mm or gauge 25 and 0.6mm or gauge 24.
Just get from either excelroof, puyat, philmetal or union. Safe ka sa apat na companies na yan sa kapal. Avoid other companies because they just import from china and usually substandard sa kapal and quality. They maybe cheap but mas maaga rin ang pag palit ng roof mo