RFID is transfer by magnetic and electronic coupling, possessed its own nature and limitation.
Under Certain Environment, could be defect. Some resolution can take special processing to make up. Some of them can not.

RFID wave can not pierce through Metal Sheet, whatever UHF, HF or LF.
When reader and tag are at the same size of metal sheet

    LF tag can function normally, get not effect by metal.
UHF and HF have to use Anti-Metal tag.( Like HYTSM03 Hyintech UHF Anti-Metal tag)
    2.4G Wave effected by metal too, just Like UHF.  However, since the tag is active, no need for special resolution.

However, the principle for HF and UHF acting on metal is different.

For HF, its Electronic Coupling, when metal meet it, just absorb.

For UHF , Metal redirect and reflect the wave.

Application Examples
1) Parking Access Control System
 On Vehicle windscreen, there is a metal film which could block the UHF wave.
In parking system, if using windscreen tag (HYG62), the best position is stick on top central of windscreen, where is not covered by this metal film

2) Jewelry Management
Jewelry is made of metal, which could absorb the power of HF wave.
And the Jewelry tag have to be small.(anti-metal tag is big).
Hyintech have solved this problem perfectly, by using High RF power Reader HI-H4W1T and Sensitive Tag HYTSJ15. When tag HYTSJ15 bind to jewelry put on plate, upon antenna HYP3242, all tags will be read. Also can be with handheld antenna HYH121535
(More Detail, Please check the Resolution Sector “Jewelry Management”)

3) When Product is made of Metal or covered by metal sheet.
Our HI-M03 is the anti-Metal tag, which could be mounting on metal surface, which is with special design for wave correction.

However, the principle is, leaving the tag the far away from metal the better.

Anti Metal tag is with relative higher cost than ordinary tag. And have to be with bigger size.