I'm going to him/her
I’m going to bring him some.
Je vais lui construire un palais.
I'm going to build him a palace.
— Astérix & Obélix : Mission Cléopâtre (2002)
I'll call him.
Je vais lui donner un coup de main.
I'll give him a hand.
Je vais lui laisser un message.
I'll leave him a message.
Je vais lui régler son compte.
I'll settle the score with him.
I'll talk to him about it.