I already have a shure sm57 and im thinking if i mic my amp up with another mic i'll get a fuller sound and more ambience , so UG what do you suggest? I can spend about £100 ($150)

one more question , why do some people recommend condesner mics to record electric guitar? I thought they were for vocals and acoustics
i'd go for a condenser; much better sound quality. and they can be used for recording anything; snails if you want to.
You like it
Condenser mics can work with anything. I occasionally use them for getting a second guitar track just as a room mic. Sounds wicked.
Yeh condenser mics are good as ambient mics, placed a little further from the guitar speaker, to give a more fuller sound.
My gear:

Gibson Les Paul Custom
Gibson Les Paul Studio
PRS McCarty 10 Top
JCM900 Head and 1960B
Dunlop Crybaby 535Q
Korg Pitchblack
Small Clone
Boss GE-7

Check my band
Samson C03. Recommending it from personal experience. Superb, especially for the money.

Recorded the entire song on my profile with it, if want to check out the quality.

It's a tad noisy which might bother you. I run almost everything through iZotope RX so it doesn't bother me.
Epiphone Elitist SG (Serious)
Tokai Silver Star
Epiphone Dot
Epiphone Les Paul
Washburn J28SCEDL
Washburn J12S

G.A.S List

JCM600 (Yes a 600..)
Is this for recording? If so, then a condenser mic has the potential to be a good investment. You'd need to shop around and make sure that the mic that you're buying can handle the decibels that you are chucking out and you'd need a phantom power source. Experiment with positioning and isolate the mic and cab (a duvet over the whole lot is a cheap solution) to prevent the sound bouncing back.

If you're talking about miking up a cab for live playing, then I'd stick with the SM57.

I mess about with recording at home and do live sound for a band but I'm no expert, so I'd recommend a trawl of recording and music tech sites unless you can find a shop that can give you good advice rather than just sell you what they've got.
its for home recording , and i never really crank up the amp (neighbours and a baby in the house), but from the looks of reviews im probably gonna go with what Willieturnip recommended and get the Samson c03
Yeah, just had a quick look at a review of the Samson and I reckon that would do the job - in fact I'm wishing that, at that price, I'd bought one!!

Ibanez SZ720FM (Duncan Distortion and a 59)
Fender 60s (Mex) Strat - (SD vintage pups)
Blackstar HT5
EHX Metal Muff
Digitech Weapon
They really are very good and I'm not just saying that because I have one. It's far from my only mic but 9 times out of 10 it's what I reach for.
Epiphone Elitist SG (Serious)
Tokai Silver Star
Epiphone Dot
Epiphone Les Paul
Washburn J28SCEDL
Washburn J12S

G.A.S List

JCM600 (Yes a 600..)