[pinkpanther]

How can it be a metaphor when the Lord literally says "lending"?

Let's go to tafsir explanation 

O you who have believed, if you support Allah, He will support you":

This part of the verse calls on believers to actively aid Allah's cause, which is understood to be the propagation of Islam and the defense of the Muslim community. 

"and He will make your feet firm":
This refers to Allah granting believers steadfastness and strength in their endeavors, particularly in times of conflict. 

So Allah needs the help of his believers. He is not powerful after all