The crimp of the bottle cap engages with the lip of the bottle. This creates many points in contact with the bottle that can exert an equal and opposite force of the gas trying to escape. The cap is held in tension against the force applied by the pressure equally against the cap. The malleable cap will deform if torque is applied, freeing the contents to fill our glasses.
C_Skadi t1_j6ashc6 wrote
Reply to ELI5: How does a beer bottle top stop the gas in the bottle from escaping enough for it to remain fizzy for extremely long times? by trumps_baggy_gloves
The crimp of the bottle cap engages with the lip of the bottle. This creates many points in contact with the bottle that can exert an equal and opposite force of the gas trying to escape. The cap is held in tension against the force applied by the pressure equally against the cap. The malleable cap will deform if torque is applied, freeing the contents to fill our glasses.