cid makes a couple good points, but all that depends on the grade of the aluminum, just like there are different grades of steel A36 being the most common mild steel, and moving up to the iron that has high alloy content like armored plating. the more "pure" aluminums will have a lot of give to them, they flex & get hung up. as you start moving up the scale to the alloys they become much stronger, and much more expensive. steel is good and inexpensive.

this is the common grade aluminum that is just run of the mill, i use it for stuff that is not structural and certainly not for a skid plate, it will just get trashed.

5052 This is the highest strength alloy of the more common non heat-treatable grades. Fatigue strength is higher than most aluminum alloys.In addition this grade has particularly good resistance to marine atmosphere and salt water corrosion. It has excellent workability. It may be drawn or formed into intricate shapes and its slightly greater strength in the annealed condition minimizes tearing that occurs in 1100 and 3003. Applications: Used in a wide variety of applications from aircraft components to home appliances, marine and transportation industry parts, heavy duty cooking utensils and equipment for bulk processing of food.

T-6 is what i used when i was building baja racers.

6061 This is the least expensive and most versatile of the heat-treatable aluminum alloys. It has most of the good qualities of aluminum. It offers a range of good mechanical properties and good corrosion resistance. It can be fabricated by most of the commonly used techniques. In the annealed condition it has good workability. In the T4 condition fairly severe forming operations may be accomplished. The full T6 properties may be obtained by artificial aging. It is welded by all methods and can be furnace brazed. It is available in the clad form (“Alclad”) with a thin surface layer of high purity aluminum to improve both appearance and corrosion resistance. Applications: This grade is used for a wide variety of products and applications from truck bodies and frames to screw machine parts and structural components. 6061 is used where appearance and better corrosion resistance with good strength are required.