Is lyric poetry one of the longest kinds of poetry?
Lyric poetry tends to be relatively sort. It's epic poetry that tends to be quite long (a subset of narrative poetry) and includes the longest poem in the world.
There are three genres of poetry:
Lyric poetry deals with the writer's state of mind, feelings, emotions, and perceptions. One example of this kind of poetry is the English sonnet (which typically are not long at all).
Dramatic poetry tells a story - a drama - in poetic verse. Entire Greek plays are written this way, as are dramatic monologues in plays.
Narrative poetry is like a novel, but in poetry. There's plot, characterization, setting - but all done within metre, rhyming scheme, and the like. Types of this kind of poetry are the "ballad" and the "epic poem".
It's within the category of the epic poem that we find really long poems. For instance, the longest poem in the world is the Mahabharata at 1.8 million words (220,000 couplets) and contains within it the Hindu classic Bhagavad Gita (which is a book unto itself) and also a philosophical work and tells the story of a war between two families/clans. To compare, the Iliad and the Odyssey - 2 epic poems that deal with the Trojan War and the return trip home - taken together is only one-tenth the size of the Mahabharata.