Citigroup (C - Get Report) and Goldman Sachs (GS - Get Report)  reported earnings today before the market opened.

With JPMorgan (JPM - Get Report) , Wells Fargo (WFC - Get Report) , and PNC Financial (PNC - Get Report)  reporting earnings last week and Bank of America (BAC - Get Report)  set to report tomorrow before the market opens, earnings season is officially here.

RELATED: BANK EARNINGS CHEAT SHEET

Even if you don't own a bank stock you should be paying to attention to their earnings, as ActionAlertsPLUS Research Analyst, Zev Fima, explains:

"Bank earnings provide a unique perspective on both the domestic and global economic backdrop. Banks are uniquely positioned to discuss consumer and business sentiment across industries because they are the money centers extending lines of credit. As a result of this they have direct insight into demand for borrowing, and you don't borrow more when you are fearful of an economic slowdown."

A few of the metrics that investors should watch out for are Net Interest Margin, Tangible Book Value, and Loan Growth.

RELATEDMORE KEY METRICS

When it comes to the banks themselves, something investors are going to want to look out for is investments in technology and digitization. Fintech is increasingly pushing deeper into what has traditionally been the banking industries space. As a result, banks need to compete by investing more in technology, which is a key reason Goldman Sachs and MasterCard  (MA - Get Report) teamed up with Apple (AAPL - Get Report) to create the Apple Card.

With earnings season about to kick into high gear, get ready by watching a replay of Jim Cramer's exclusive video-conference call with members of his Action Alerts PLUS club for investors, in which he unveiled his "5 Rules for Trading Stocks During Earnings Season."

JPMorgan, Citigroup, Goldman Sachs and Apple are holdings in Jim Cramer's Charitable trust portfolio. Want to know when Jim buys or sells shares of JPM, C, GS, or AAPL? Sign up for a free trial now.