Usage patterns
額をぶつけるto bump/hit one's forehead (on something)
I accidentally bumped my forehead on the door.
額に手を当てるto put one's hand to one's forehead (e.g. to check a fever)
The mother put her hand on her child's forehead to check for a fever.
額の汗をふくto wipe the sweat off one's forehead
He wiped the sweat off his forehead with a towel.
額にキスをするto kiss someone on the forehead
The father kissed his daughter on the forehead.
Expressions
猫の額tiny area; tiny surface; cat's forehead 額を集めるput heads together; gather for discussion; huddle 額を寄せ合うput heads together; gather for discussion; huddle