Guys like to feel strong and in charge. Things like "nice arms" or "wow ur sooo strong" is what they wanna hear lol
Telling a skinny nerd, "you have nice arms", or "wow your so strong" will lead to high levels of awkwardness.
If it is a guy who spends a lot of time at the gym, they may think "yes, my workout routine is paying off. Chicks digging it."

