Making a blinking light seems to be one of the most common beginner projects with Arduino. A typical approach is to connect an LED + resistor (in series) to an IO pin, and connect the other end to ground. In code, you make the pin an output, and bring it
LOW repeatedly to flash the LED.
What happens if you leave that resistor out? Obviously you're going to wreck the LED, but will it also damage the Arduino in some way?