Citigroup stock is soaring Wednesday after the big bank topped earnings expectations and unveiled a massive stock buyback program. Here's why that's important.

Citigroup (C) reported fourth-quarter results that exceeded expectations, sending shares higher in pre-market trading Wednesday. Citi's net income for the fourth quarter was $2.86 billion, up from a loss of $1.

Citigroup ( NYSE: C) stock gained 5.6% in Wednesday premarket trading after the megabank posted better-than-expected Q4 results and approved a $20B stock buyback program. Furthermore, the company expects its net interest income to rise in 2025.