The role of the Monarch is not easy to qualify. She is a symbol of continuation, stability and unity. Her neutrality makes her look like she is doing exactly nothing, when it's the source of her power and influence. She lives above politics.
Beyond that, the Queen has real so called reserve powers that in theory she could use in time of great crisis to change government or stop laws (she used it once I think). But she can't use them in an authoritarian manner or else risk losing them and tarnish her legacy.
