What is the form of the poem "Evening Primrose" by John Clare, for example is it a sonnet, ode est.?Are there any metaphors or similes used? What is the effect?
John Clare, as a farmer-poet, rarely used formal poetic forms, and this poem is no exception. Although it is fourteen lines long (the usual length for a sonnet), the rhyme scheme does not correspond to any sonnet patterns, nor do the lines contain (or vary in any significant way) from iambic pentameter. The lines are rhymed couplets in iambic tetrameter.
Odes typically invoke a specific force or power, speak to it, entreat it, or (in the case of Pindaric odes) commemorate some military/political/social triumph. As this poem does none of those things, it is not an Ode either (you can usually recognize Odes by their second and third-person perspectives).
I would posit, at the risk of being contradicted by a John Clare scholar, that this poem is simply a descriptive lyric.