Yeah, this one's common. You're probably pushing way too hard. Excessive pressure doesn't speed up drilling, it just grinds down your drill bit and strains the tool's gears.
Fix: Ease up. Let the tool do the work. For metal, always start with a center-punch indent to keep the bit from slipping. Use a cutting lubricant on most metals (except iron and brass—drill those dry). If the speed comes down extremely, reduce the load or stop the tool to avoid damage.
If that didn't work, you might be using the wrong speed setting for the material. Remember: Low (1) is 0-500 RPM for high-torque work like driving screws. High (2) is 0-1,900 RPM for faster drilling. Switch to the low setting if you're driving large screws or drilling tough material.
Heads up: That grinding noise is the sound of your tool's service life getting shorter. If the noise persists after correcting your technique, stop using it and get it serviced.