The net loss was equal to $1.74 a share, compared with a profit of $915 million, $1.26 a share, in the year-ago period.
The loss included $1.8 billion in derivatives losses. Derivatives are a type of structured investment tied to the value of underlying assets.
Excluding the losses, MetLife's operating earnings were $723 million, or 88 cents a share, compared with $887 million, or $1.22 a share, in the year-ago period.
Analysts on average expected MetLife to post operating earnings of 68 cents a share, according to Reuters Estimates.
Shares closed up 4 percent at $33.57 on Thursday but were flat in after-hours trade.
(Reporting by Lilla Zuill; Editing Bernard Orr)