She claims the manifesto to be a plan for "a stronger, fairer, more prosperous Britain", writes Catherine Feore.
All sides have recognised in the House of Commons that social care needs more money, particularly given the country's ageing population.
Mrs May described the plan as "declaration of intent" to tackle the "great challenges of our time".
It reaffirms the prime minister's earlier commitment to leave the European single market and customs union when Britain leaves the European Union.
She also set out on Thursday plans to give workers a voice on company boards, either through a nominated director from the workforce, the creation of an employee advisory council or a designated non-executive director.
She promised that her government would be "relentless in tackling burning injustices" and would govern for "mainstream Britain".
"We do not seek to be half-in, half-out", she said, referring to a "clear choice" made in last year's referendum in favour of Brexit.
She said: "Margaret Thatcher was a Conservative, I am a Conservative, this is a Conservative manifesto", said the Prime Minister.
"So we will work with like-minded countries to change the rules so that they are updated and better reflect the breadth of our assistance around the world".
She warned that making a success of Brexit would not be easy.
Gold rises to two-week high as Donald Trump's troubles multiply
Department of Labor, also released on Thursday, said initial jobless claims fell by 4,000 to 232,000 in the week ending May 13. Gold prices pared gains as the USA dollar came off its lows and US 10-year Treasury yields bounced up from a 1-1/2-week low.
She said she would tighten laws on company takeovers and would ensure any foreign group buying important infrastructure did not undermine security or essential services. "The Conservatives' record is one of broken promises and failure", he said. Net migration (the difference between people coming to the United Kingdom for more than a year and those leaving) was 273,000 in the year to last September.
The manifesto also moots a review of the cost of energy; support for shale gas and more money for communities where fracking goes ahead; bringing fuel poor homes up to band C energy efficiency standards by 2030; and another look at energy efficiency standards for new build properties.
May: "The Conservative party has always been on the centre ground". While Thatcher mistrusted the state, May's election manifesto says that "government can and should be a force for good", and outlines a more interventionist role in business and industrial strategy.
A Labour Party spokeswoman said: "We are grateful to all those who donate to the Labour Party and are supporting our General Election campaign".
She promised that the Conservatives would be "upfront and honest about the scale of the task we face".
She said a strong economy and delivering Brexit are her top priorities.
"There is good solid Conservatism, which puts the interests of the country and the interests of ordinary working people at the heart of everything we do in government", she said at a news conference to launch the Conservatives' policy pledges before a national election she called for June.
"Every vote for me and my team will strengthen my hand in the negotiations to come", May said at the launch in Halifax in northern England, calling it "a manifesto to see us through Brexit and beyond".
"We will focus on creating extra capacity on the railways, which will ease overcrowding, bring new lines and stations, and improve existing routes - including for freight".