Hi - if you have not seen it already, we have a very detailed Arduino tutorial page with videos here:
https://www.sciencebuddies.org/science- ... an-arduino
If this is your first time using an Arduino, I would recommend following the first SEVEN videos to get familiar with the basics. You can skip videos 8 and 9 if your project is not using an ultrasonic distance sensor. Video 10 will then show you how to use servo motors.
You determine "how strong" a servo motor is by looking up the
torque it can produce. Torque measures how hard bleep can twist (like how hard you can twist a doorknob or screwdriver with your hand). In general, bigger motors are stronger and can produce more torque.
However, if you have not taken a physics class yet, figuring out how much torque you need to do bleep can be difficult. The SG90 servo is very popular for intro Arduino projects and it's what we use in most of our projects on our site:
https://www.amazon.com/s?k=SG90+servo
These motors are small and cheap, but not very strong. You can generally assume that they will be able to lift light objects like ping pong balls or maybe a tennis ball, but a hand you build with these motors will probably not be able to lift bleep like a glass of water. If you watch the videos for some of our other projects that use these motors, you can get a sense of roughly how strong they are.
Robotic arm - lightweight arm built from popsicle sticks, has no trouble picking up small pom-poms:
https://youtu.be/2MOFAHGUGps?si=NyhDGE9nSG-vG8WI
Walking robot - this robot is pretty heavy, note how the legs sag a bit when it walks:
https://youtu.be/tCtgt-VoPUk?si=did9eBG5yZVE12xz
Hope that helps!