Police chiefs could hire people leaving the armed forces as firearms officers, Met Commissioner Sir Ian Blair says.
Sir Blair called for change within the police force
Other roles that could be filled short-term by people with pre-existing skills included underwater searches and financial investigation, Sir Ian said.
Radical changes were needed if police were to tackle crime and terrorism, he told the Police Superintendents' Association conference in Warwickshire.
He said the London bombings had been a "wake-up call to all of us".
Sir Ian said the police must be "bold enough" to see whether some police functions could be done by people on short-term contracts.
He said: "Could we bring staff directly in from the armed services, to use that just as an example, give them a small amount of basic training and then clear instructions as their role on firearms duty?"
People on short-term contracts could include surveillance officers, financial investigators, mounted officers and underwater search teams, he suggested.
Sir Ian said the question was "how bold we want to be and how far we can go" without losing the flexibility of officers' deployment or making police jobs less interesting.
Such negative effects "would be a mistake in terms of the people we want to join us", he said.
He said that the London bombings meant police had to consider whether the present structures, methods and "way we reward" could "sustain a proper response to international terrorism on our streets".
Sir Ian said this response required far more intelligence analysis, more firearms officers and a "far greater simple presence on the streets".
He asked: "Can we do all that about counter-terrorism at the same time as continuing to deal, for instance, effectively with anti-social behaviour?
"I don't think we can unless we change. Unless we are bold, we are inclusive, we are determined to bring change about."
The Met chief also called for greater flexibility around pay and conditions - he said pay should be decided on a local or regional basis, rather than police negotiating national rates.
Community support officers should get the same basic five weeks' training as constables, he added.