In this study the adhesion properties of a geopolymer-based adhesive on metallic substrates are investigated, considering different surface conditions. Mechanical treatments (grit-blasting and sand-blasting) and chemical treatments (nitro-phosphoric acid and silanization) were performed on steel and aluminium plates. Single lap joint specimens were tested in order to access the influence of these pretreatments on the shear bond strength. The surfaces were scanned and the average surface roughness parameters were used in order to assess their effect on bond strength. The results indicated that the effect of individual surface roughness parameters alone is not statistically significant when correlated with bond strength. In general, chemical treatments were usually less effective than mechanical treatments alone for both steel and aluminium joints with geopolymers as adhesives.