Use 'call upon' for serious or official requests, especially during events or in writing.

Formal Requests

'Call upon' often happens in speeches to engage the audience or ask for action.

Public Speaking

Using 'call upon' can suggest urgency or importance of the favor or assistance needed.

'Call upon' for visits indicates politeness and is less casual than 'drop by'.

When 'calling upon' someone, it suggests a planned and intentional visit, not spontaneous.

'Call upon' for skills or knowledge means to intentionally utilize one's internal resources.

Use 'call upon' to describe how someone responds to a challenge by using personal abilities.