“Help” in the sentence “Help me!” is an imperative verb.
a verb in the imperative mood
People resented his imperative tone of voice.
… I have begun to feel each time as if I am mutilating my antennae (which is how Rastafarians, among others, think of hair) and attenuating my power. It seems imperative not to cut my hair anymore. —Alice Walker, Living by the Word, (1981) 1988
This strange and distorted form of breathing could be interrupted for a minute or two by a strong effort of will, but would then resume its bizarre and imperative character. —Oliver Sacks, Awakenings, 1973
We had a long and interesting evening with the Katzenbachs. He and Lyndon discussed the imperative need to make Washington a law-abiding city and how to go about it. —Lady Bird Johnson, 27 Jan. 1965, A White House Diary, 1970
She considers it a moral imperative to help people in need.
“Eat your spinach!” is in the imperative.
“Go” and “buy” are imperatives in the sentence “Please go to the store and buy some milk.”
Ellroy has got to be the only writer who still uses “dig” as an imperative … —Laura Miller, New York Times Book Review, 20 May 2001
Indeed, under pressure from a new way of life in which radiant heat from woodburning stoves must circulate unimpeded by dividers, virtually every house with a chimney today has abandoned the closed-door imperative of the high-technology kitchen. —Maxine Kumin, In Deep, 1987
“Maturity” had been a code word … for marriage and settling down; “growth” implied a plurality of legitimate options, if not a positive imperative to keep moving from one insight or experience to the next. —Barbara Ehrenreich, New York Times Magazine, 20 May 1984