فَتَحَ الْبَابَ لِلْعِلْمِ.
He opened a door to learning.
If the expression refers to creating access to education, “opening a door” may be figurative. If a library door is literally being opened, an ordinary literal reading may be sufficient.
Calling the expression metaphorical merely because “door” occurs ignores the contextual cue. A stronger answer compares both readings and explains which is supported in the given setting.