What are the spears of the stars and what are the tears?

These two lines are generally believed to be an allusion to John Milton's Paradise Lost, specifically these lines:

They, astonished, all resistance lost,All courage, down their weapons dropt.

Here, Milton describes the fall of the angels who allied themselves with Satan before God created the world. As they find themselves defeated, they surrender. In "The Tyger," Blake is asking us to consider, "Did he who made the Lamb make thee?" The question, "what immortal hand or eye..." is not a rhetorical one. Blake is asking whether it is possible that God could have made two such disparate beasts, or whether it is possible that Satan had a hand in designing the ferocity of the Tyger.
In Blake's poem, the "stars" seem to represent these angels, throwing aside their weapons and weeping at the sight of the Tyger. Blake questions whether God smiled upon his work, knowing that it had occasioned defeat in those who followed Satan—or whether Satan smiled upon it, after all.
There are many allusions in "The Tyger." Very little about it is straightforward, and the use of metaphor can often seem nonintuitive. It is important to appreciate the poem in the context of the many intertextual references Blake uses to explore the ferocity and strangeness of his Tyger. I have attached a link below to an interesting resource on the topic.
https://www.bl.uk/romantics-and-victorians/articles/an-introduction-to-the-tyger

The term "spears of the stars" is a poetic way of saying lightning. Likewise, the "tears" coming from heaven are rain. These are both examples of metaphor, which is comparing two different things without using the words "like" or "as." Here, Blake compares lightning bolts to spears, and we can understand that the bolts do look like spears coming down out of the sky; and if one strikes you, it can harm or kill you, just as a spear can. We can also easily understand how rain can be compared to tears.
These two images also personify nature. Nature doesn't throw spears, only human beings do. And the clouds don't cry; crying is a human emotion. Blake, filled with wonder over the creation of so fierce an animal as a tiger, is attributing human qualities to nature, as he is also wondering what God's emotional response to the tiger is: does God "smile" over the tiger?