We
 report a systematic comparative dispersion-corrected DFT study of 
single (K, Au, and Pt) atoms adsorption over a wide range of 
metal-supported oxide ultrathin films (MgO on Ag and Mo, ZnO on Cu, Ag, 
and Au, SiO2 on Pt and Ru, TiO2 on Ag and Pt, ZrO2 on Pt and ZrPt). 
These films include reducible and non-reducible oxides, and have been 
prepared and characterized experimentally, showing very unusual and 
interesting behaviour towards metal atoms adsorption. 
The interaction of
 K and Au with the metal/oxide substrates is dominated by 
charge-transfer aspects, where K tends to assume positive charge and Au 
negative charge. 
This fact reflects into a general trend where 
metal-supported oxide films displaying large work function (i.e. deep 
empty states) tend to bind K cations strongly, while supports with small
 work function (i.e. shallow donor