Capital One and Discover completed their merger on May 18. Discover what financial professionals say you should do to keep your money secure.

Federal regulators approved Capital One's $35.3 billion acquisition of Discover Financial Services earlier this year despite opposition from consumer advocates and some top Democrats, who cited concerns about reduced competition, financial stability and potential harm to low-income consumers and those with poor credit scores.

Capital One finalized its $35.3 billion purchase of Discover on Sunday, completing a credit card mega-merger announced more than a year ago. Nothing will immediately change for Discover customers, according to a press release issued Sunday by Capital One.