Metropolitan Life Insurance Co., one of the country's biggest life insurers, is betting big on banks. The company announced plans Thursday to acquire Security First Group, an annuity manufacturer and third-party marketer through banks, for $377 million. In addition to selling its annuities directly to 16 banks, Security First provides an array of support services to 60 smaller banks around the country. The deal comes as major insurers are grappling with how best to sell their wares through banks. MetLife last year set up its own bank distri- bution division, but it has signed up only one bank. "We saw it as an opportunity to jump-start what was an incubator project," said Joe Reali, senior vice president for MetLife's department of bank financial services. By buying Security First, which is owned by London (Ontario) Insurance Group, MetLife could build a powerful bank presence, competitors said.