BET method is preferred choice for higher relative surface areas like porous materials, activated carbon ,quantum dots materials,graphene and nanosized metal oxides.I thinck the Lanqmuir model is compatible with metals which have low relative surface areas.
really I found many papers in which surface area of metal powder was measured using BET, So I want to see if that is correct , this is the reason of my question
BET theory used to describe specific surface area of all porous materials. The correctness of measured specific surface area depends on porosity type. For instance, BET method is widely applied on microporous material , although it's assumptions do not take into account micropore filling and despite its incapability to measure the surface area of such materials in accurate value. You can try and compare between both methods .