twist (one's) arm
To pressure or force one into doing something. Oh, she immediately agreed to come tonight—I didn't even have to twist her arm. They had to twist my arm to convince me to start volunteering, but when I finally did, I realized how much I loved it.
twist someone's arm
Fig. to pressure someone. (Fig. on the image of hurting someone until they agree to cooperate.) I had to twist her arm a little, but she agreed. Do I have to twist your arm, or will you cooperate?
twist (someone's) arm
Slang To pressure or coerce: If you twist my arm, I'll stay for a second beer.