This chapter introduced David as a soldier, a skill that will be important for the rest of his life.
Trust in God is more powerful than physical might or military training and equipment. David, trusting in the Lord and armed only with a sling, defeats Goliath who is well-armed and physically strong but who did not believe in Yahweh. (See: rc://en/tw/dict/bible/kt/trust and rc://en/tw/dict/bible/kt/believe)
The people of Israel often used the term “uncircumcised” to refer to Gentiles. Here it is used to describe the Philistines. (See: rc://en/tw/dict/bible/kt/uncircumcised)
David uses rhetorical questions to state his desire to fight the giant: “What will be done for the man who kills this Philistine and takes away the disgrace from Israel? Who is this uncircumcised Philistine that he should defy the armies of the living God?” (See: rc://en/ta/man/translate/figs-rquestion)
His brother uses rhetorical questions to show his disdain for his younger brother, whom he thinks is pretending to be bigger than he really is: “Why did you come down here? With whom have you left those few sheep in the wilderness?” David defends himself with some questions: “What have I done now? Was it not just a question?”
Goliath also uses a rhetorical question to show his contempt for young David: “Am I a dog, that you come to me with sticks?”