Shares of General Motors Co. /zigman2/quotes/205226835/composite GM -0.06% sank 3.0% in premarket trading Monday, after nearly 50,000 United Auto Workers employees went on strike. The strike shut down 33 manufacturing plants in nine states and 22 parts distribution warehouses. GM said over the weekend that it has presented a "strong offer" to UAW leadership and that it was "disappointing" the union chose to strike. GM said its offer includes over $7 billion in investments and more than 5,400 jobs, including "solutions" for unallocated assembly plants in Michigan and Ohio. The UAW said things it was trying to secure by going on strike include fair wages, affordable healthcare and a share of profits. The UAW also called out the other two of the Big 3 automakers to "recognize the contributions and sacrifices the UAW members made to help support the industry. Shares of Ford Motor Co. /zigman2/quotes/208911460/composite F +1.98% slipped 0.7% ahead of the open and Fiat Chrysler Automobiles N.V. /zigman2/quotes/204248628/composite FCAU +0.61% were still inactive. GM's stock has rallied 16.2% year to date through Friday while the S&P 500 /zigman2/quotes/210599714/realtime SPX -0.39% has advanced 20.0%.