The 64-year-old rocker said he hopes that Brucknell goes far in the competition, despite the fact she has been unpopular with viewers.
Writing on his website, he said: 'Kitty, try looking at what they said about Freddie Mercury when we started out. Jealousy is a powerful emotion – it turns people into beasts. They are all wishing they were you.'
May added that he really enjoyed her rendition of the classic Queen track Who Wants To Live Forever on the first live show.
He said: 'Thank you, Kitty, for putting your heart into it in such an individual way. Go Kitty!'