What is the theme for both "The Tyger" and "The Lamb" by William Blake?
The Tyger and the Lamb are poem from Blakes's collection of poetry called "Songs of Innocence and Experience". That is a good bit of knowledge to keep in mind when determining the themes for the poems.
The next step would be to look at the diction, word choice, for each poem. What sorts of words are used? "burning" "bright" "night" all connote a sense of darkness mixed with heat and passion.
Imagery is also important in determining theme (although the word you are probably looking for is tone). What contrasting images do the poems use?