Question: We know through [General Relativity](http://en.wikipedia.org/wiki/General_relativity) (GR) that matter curves spacetime (ST) like a "ball curves a trampoline" but then how energy curves spacetime? Is it just like matter curvature of ST?

Answer: 
Theoretical viewpoint:
----------------------

Einstein field equations can be written in the form: $$\color{blue}{G\_{\mu\nu}}=\color{red}{\frac{8\pi G}{c^{4}}} \color{darkgreen}{T\_{\mu\nu}}$$
We can write in simple terms: $$\rm \color{blue}{Space-time \,\,geometry}=\color{red}{const.}\,\,\color{darkgreen}{Material \,\,objects}.$$
And the $T\_{\mu\nu}$ is a mathematical object (a tensor to be precise) which describes material bodies. In that mathematical object, there are some parameters such as the density, the momentum, mass-energy... etc. So it is those parameters that determine 'how much space-time curvature' is around a body. And one of the parameters is of course *energy*. Therefore, *energy* do bend space-time.

Experiments that confirm this point:
------------------------------------

First, do photons have mass? The answer is an emphatic **'no'**. The momentum of a photon is $p=\frac{hf}c$, and from special relativity: $$\begin{align}E=\sqrt{(mc^2)^2+(pc)^2}&\iff E^2=(mc^2)^2+(pc)^2\\&\iff E^2-(pc)^2=(mc^2)^2\\ \end{align}.$$
The energy of a photon is: $E=hf$ which is an experimental fact. It can also be expressed as $E=pc$ since $E=hf=\frac{hf}{c}\cdot c=pc.$ Therefore, $E^2=(pc)^2$ and so $E^2-(pc)^2=0$. Putting this in our previous derivation we get: $E^2-(pc)^2=(mc^2)^2=0$. Since $c^2$ is a constant, then $m=0$. Therefore, photons have no rest mass.

**Claim:** Photons are not subject to gravitational attraction since they have no rest mass.

**Experimental disproof:** [Gravitational lensing](http://en.wikipedia.org/wiki/Gravitational_lens):   

 ![copyright to the author](https://i.stack.imgur.com/exReS.jpg)

You could see light being bent due to the presence of a strong gravitational field. 

**Conclusion:** Even if light has no rest mass, it has energy and momentum. And it is being attracted due to gravity, so the natural conclusion is that energy do curve space-time.
The source of gravity in GR is not just mass, but the full energy-momentum tensor; this tensorial quantity is a measure of energy, momentum and stress, and applies to ALL forms of matter and all fields that are non-gravitational. Furthermore, there exists a quantity in differential geometry which is automatically conserved in a small neighbourhood on a differentiable manifold, called the Cartan moment of rotation - it turns out that this is mathematically just the dual of the Einstein tensor, and what GR does is relate these two tensorial quantities. This is what the field equations tell us - that the geometry of space-time is related to its energy-momentum content.