William Blake is considered one of the major Romantic Poets of the first generation.
His "prophetic books", together with his engraving and painting, are amongst the greatest representations of the Romantic attitude towards nature, and also towards the negative effects of Industrial Revolution, such as urbanization, corruption and a physical as well as a metaphorical "pollution" of cities and souls.
The Lamb (from Songs of Innocence) displays the condition of Nature in the Garden of Eden, before the Fall. The Lamb is a symbol of purity and innocence, of childhood and generosity, as well as a symbol of Christ.
The Christian interpretation of Blake's symbolism is very strong and complememtary with a more pantheistic view of Nature as an organic living whole.
The poet prophet emphasizes a dual vision of God, who was able to create the Lamb but also the Tyger (from Songs of Experience), which is the expression of the so-called "sublime": majestic, fearful and fascinating perfection. The power and the frightening symbol of the Tyger seems to be a challange for God Himself and it's a juxtaposition between the beautiful and idyllic Lamb and the potentially fatal power of the scaring creature of darkness that may eventually claim to be created by the same God. Lamb and Tyger are two sides of the same coin, as well ad Songs of Innocence and of Experience, which represent Blake's insight into the Universe.

- William Blake (Part 1 of 2): The Lamb (Songs of Innocence) concernes an introduction of the Poet and his main themes, ad well as a detailed analysis of "The Lamb"
https://youtu.be/r81D5HvUhls

- William Blake (Part 2 of 2): The Tyger (Songs of Experience) concernes a detailed analysis of "The Tyger" and an explanation of "London" and "The Chimney Sweeper"
https://youtu.be/fs5QVHcyRDs