Albert Barnes Commentary Psalms 104:21

"The young lions roar after their prey, And seek their food from God." — Psalms 104:21 (ASV)

The young lions roar after their prey - This is a continuation of the description in the previous verse. At night the beasts which had been hidden in the daytime emerge and seek their food. The lion is particularly specified as one of the beasts that in a general survey would attract attention. The psalmist hears his roar as he goes out in the forest in pursuit of his prey.

And seek their meat from God - Their food. That is, God gives it to them, and they act as if they sought it from him. They seek it where he has placed it; they are dependent on him for it. It is a beautiful idea that even the animal creation act as if they called on God, and sought the supply of their needs from him.