[DonRotolo]

For metal, particularly aluminum, the chips are your enemy. Even with the right bit, the metal tends to get soft and stick to the bit, leading to bit failure a few seconds later.

You will have better results if you can spray coolant or at least a good amount of compressed air onto/near the tip of the bit, so the chips are kept away from the cutting area. By all means, a vacuum attachment is essential.

Cooling? Not necessarily a stream of liquid (with makes a mess...), but look into air-powered chillers (they use just cold compressed air) or mist sprayers (a fine mist which doesn't make a mess).

Naturally, slow it down (feed speed) for metal as compared to wood. Experiment, take notes to see what works best, and don't fret if you break a bit.

Holding down metal for machining is a LOT harder than wood, the requirements are much greater. Screw it down in several places - clamps will not work as well as you think.