Warm water means warm water. Use lukewarm water. It could shatter your car's window.
Pour warm water over a frozen door, latch, or frame. Pour warm water around the door seal and handle.
Ice scraper. Metal objects can damage a vehicle. Most ice scrapers are double-sided. Double-sided is great for snowy windshields.
If you don't have a plastic ice scraper, try a spatula, credit card, etc.Apply lubrication to frozen area. You can open your door after the ice melts.
In winter, give these approaches more time. Keep a pitcher, snow scraper, and de-icer accessible.
You'll thank yourself. Some of these happen away from home, so be ready.