May is unable to get the 326 seats her Conservative party needs for an outright majority.
The DUP are pro-union in United Kingdom terms, pro-Brexit and socially conservative. "May's departure from Downing St.is remorseless".
But rumors swirled of plots to oust May.
Former party leaders have warned any immediate leadership challenge would be too disruptive, but most commentators believe May can not survive in the long-term.
Several hundred people - many of them Labour voters - protested in central London against the alliance, with chants of "racist, sexist, anti-gay, the DUP has got to go".
Despite earlier saying that a cabinet meeting had been scheduled for Saturday, a spokesman said May would not be holding one but would name more members of her cabinet.
A Conservative Party source telling Reuters "she's staying, for now".
He acknowledged that the government would now be unable to get numerous measures promised in its election platform through Parliament.
May's gamble in calling an early election backfired, as her Conservative Party lost its majority in Parliament. However, their view of a Brexit deal might be different.
"What that would allow the DUP is to say: we are not just acting in the interests of Northern Ireland".
The DUP's social conservatism - it is opposed to same-sex marriage and abortion - has also alarmed some in May's party, particularly Scottish Conservative leader Ruth Davidson, who is gay.
These deals tend to be loose and a long way short of a formal coalition.
This deal would see the DUP promise to back the government in votes of no confidence and supply - or budget - issues.
Conservatives are predicted to win 319 seats, down 12 seats on 2015, with Labour predicted to win 261, gaining 29 seats.
Katie Perrior, who quit as May's communications chief in April, said Timothy and Hill were "great street fighters but poor political leaders" and exercised too much power over the prime minister.
The 1998 Good Friday agreement set up power sharing in Northern Ireland, largely ending years of sectarian violence.
Typically the British government tries to act as an honest broker between republicans and unionists.
Following the speech there will be a few days of debate followed by a vote on its content. By tradition, defeat on a Queen's Speech vote topples the government.
"If we are not European Union members there will have to be an arrangement - we want a tariff-free access to European Union market." he said.
"It's an issue very close to my heart and one that I wanted categoric assurances from the prime minister on, and I received (them)", said Davidson, who is engaged to be married to her female partner. "This is still on".