Which cabins have a metal fronted balcony?
On Queen Elizabeth and Queen Victoria - BF grades 4001 through to 4042 (excluding inside cabins) have metal fronted balconies.
Queen Anne has metal fronted balconies in the A1 and BF grades, and partially metal fronted balconies in the Q3, Q6 and BE grades.
This example is taken from 4042, Queen Victoria
Queen Mary 2 BU, BV, BY & BZ grades have sheltered enclosed balconies.
The following question may also be of interest to you: Which cabins have a restricted/shaded/partly sheltered balcony and what do they look like?