Long time readers will recall my post of last year on po' boy militia logistics and stainless steel water bottles.
As Wikipedia reports the good and bad of uninsulated metal as a canteen:
Metal water bottles are growing in popularity. Made primarily from stainless steel or aluminum they are very durable and retain minimal odor or taste from contents. Aluminum bottles contain a plastic resin or epoxy liner to protect contents from taste and odor transfer. Although most liners are now BPA free, older and less expensive models can contain BPA. It is not recommended to fill aluminum bottles with acidic liquids (e.g. orange juice) as this could cause aluminum to leach into the contents of the bottle. Stainless steel bottles do not contain a liner but have been known to transfer a metallic taste and odor to contents. Bottles made with food grade (Type 304 or 18/8) stainless steel do not transfer taste or odor. Depending on the type of source material and manufacturing process behind your stainless steel bottle, trace amounts of minerals can leach into contents. Metal water bottles can be heavier than their plastic counterparts and readily transfer temperature of contents to external surfaces which makes them unsuitable for use with very hot or very cold liquids.
The last sentence is a real downer, but it can be remedied by making your own insulated cover with general instructions found here:
Such totes (as in the one pictured above) can be purchased, but they are generally more expensive than the bottle itself, especially when you pay $.39 each for them at the thrift store like I do.