From meta (between) and ōps (eye/face). Literally 'between the eyes' — the forehead. In Revelation, both the seal of God and the mark of the beast are placed on the forehead, representing ultimate allegiance.
The forehead in Revelation is the place of identification — it reveals who you belong to. God's servants receive His seal on their foreheads (Revelation 7:3, 14:1), while the beast's followers receive its mark on their foreheads (Revelation 13:16). This draws from Ezekiel 9:4, where God marked the foreheads of the faithful. The forehead represents public, visible allegiance — every person will be identified by their ultimate loyalty.