Wireless charging with metal as phone cover?

Hi have a Huawei p20 and want to upgrade wireless charging my wirless charger flashes but what does it mean that he recognizes metal so it would be possible or not?

Well, apparently not. As in the phone more metal is in there than it is seen for the charge before

Yes, other people do it but synonymous with the one plus 6 is also made of metal in the back know you because more accurate?